kha filtration slime city)

8/2/2019 KHA Filtration Slime City)

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Table of Contents

AUTHORS SYNOPSIS ___________________________________________________ 5

A COMPARATIVE INTRODUCTION ________________________________________ 7

Imagine a river ___________________________________________________________ 7

Consequences of your Actions ______________________________________________ 8

THE ART OF POND FILTRATION __________________________________________ 9

Starting at the Beginning __________________________________________________ 10

DYNAMICS OF A FISH POND ____________________________________________ 12Nitrifying Bacteria ______________________________________________________________ 12pH __________________________________________________________________________ 12Temperature __________________________________________________________________ 13

Oxygen _______________________________________________________________________ 14Ammonia _____________________________________________________________________ 15So what now? _________________________________________________________________ 15

Stocking Densities _______________________________________________________ 16

Koi Length to Mass Ratio __________________________________________________ 18

The Effects of Koi Growth on the Pond System _______________________________________ 18

CHAPTER 1: DEFINITIONS ______________________________________________ 19

AS THEY RELATE TO KOI POND FILTRATION ___________________________________ 19

CHAPTER 2: OXYGEN _________________________________________________ 28

Dissolving Oxygen into the Water ___________________________________________ 28

Dissolved Oxygen ________________________________________________________ 28

Factors Affecting Dissolved Oxygen in Koi Ponds _____________________________________ 28Dissolved Oxygen and Temperature _______________________________________________ 29

Chapter 3: SOLIDS - ORGANIC & INORGANIC SOLIDS ________________________ 30

Pollutants ______________________________________________________________ 30

Inorganic Solids _________________________________________________________ 30

Suspended Solids ______________________________________________________________ 30Dissolved Solids ________________________________________________________________ 31

Organics _______________________________________________________________ 32

Controlling Algae ________________________________________________________ 32

Chapter 4: CIRCULATION ______________________________________________ 33

Water Circulation ________________________________________________________ 33

Importance of Internal Water Circulation ___________________________________________ 33Effects of Incorrect Circulation ____________________________________________________ 33Oxygenation and Circulation _____________________________________________________ 34Generating Circulation __________________________________________________________ 34By-Passing Filters_______________________________________________________________ 34Stagnant Water ________________________________________________________________ 35

CHAPTER 5: TURNOVER RATES & FLOW RATES ____________________________ 36


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Turnover Rate __________________________________________________________ 36

Effects of Turnover Rate on Ambient Ammonia ______________________________________ 37Turnover Rate and Ambient Ammonia _____________________________________________ 38Turnover Rate and Removal of Solids ______________________________________________ 38Turnover Rates and Dissolved Oxygen ______________________________________________ 39

Restrictions and Frictional Losses ___________________________________________ 39Frictional Losses _______________________________________________________________ 39Gravity Fed Pipes, Water Volume and Friction Loss ___________________________________ 39Overcoming Friction Losses ______________________________________________________ 40

Flow Rate ______________________________________________________________ 41

Flow Rate - Basic Principles ______________________________________________________ 41Flow Rates through Pipes ________________________________________________________ 41

Flow Rate and Mechanical Filters ___________________________________________ 41

Basic Principles ________________________________________________________________ 41Flow Rate and Restrictions in Mechanical Filters _____________________________________ 42

Flow Rate and Biofilters___________________________________________________ 42Basic Principles ________________________________________________________________ 42Summary of Flow Rates _________________________________________________________ 43

Pumps _________________________________________________________________ 43

Pump Capacities _______________________________________________________________ 43Power consumption ____________________________________________________________ 43

CHAPTER 6: MEDIA ___________________________________________________ 44

Definition ______________________________________________________________ 44

Basic Principles __________________________________________________________ 44

Media _________________________________________________________________ 44

Media Surface Area _____________________________________________________________ 45Flow Rate and Media ___________________________________________________________ 46Physical Lay-out of the Media ____________________________________________________ 46Effects on Flow Rate with Different Media in Different Chambers ________________________ 47Depth of Filter Media ___________________________________________________________ 47The Biofilter & Media ___________________________________________________________ 47

Biofilms ________________________________________________________________ 48

What are Biofilms? _____________________________________________________________ 48Where do Biofilms Form? ________________________________________________________ 48How do Biofilms Form? __________________________________________________________ 48How Strong are Biofilms? ________________________________________________________ 49

Biofilm and Flow Rate ___________________________________________________________ 49Biofilm Development ___________________________________________________________ 49Complexity of Biofilms __________________________________________________________ 50

Organics and Biofilms ____________________________________________________ 50

Slime Cities _____________________________________________________________ 50

CHAPTER 7: FILTRATION _______________________________________________ 52

Filters _________________________________________________________________ 53

Settlement Chamber/Tank _______________________________________________________ 53Open Media Filters _____________________________________________________________ 53Screening _____________________________________________________________________ 53

Closed or Pressurised Media Filters ________________________________________________ 53Sand Filters ___________________________________________________________________ 53Placing Pressurised Filters in Parallel _______________________________________________ 54


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Gravity Separation _______________________________________________________ 56

Vortexes _____________________________________________________________________ 56Multi Cyclones _________________________________________________________________ 57

Flotation _______________________________________________________________ 57

Surface Skimmers _______________________________________________________ 57

Design Parameters for Filters ______________________________________________ 58

CHAPTER 8: BIOFILTERS _______________________________________________ 59

Basic Principles __________________________________________________________ 59

Effects of High Levels of Ammonia _________________________________________________ 59pH and Ammonia ______________________________________________________________ 60

Biofilters _______________________________________________________________ 60

Nitrifying Bacteria ______________________________________________________________ 60Heterotrophic Bacteria __________________________________________________________ 61Starting up Biofilters ____________________________________________________________ 61

Seeding Filters _________________________________________________________________ 62Open Biofilters (Open media systems) ______________________________________________ 62Trickle Filters __________________________________________________________________ 62Bakki Showers _________________________________________________________________ 63Fluidized Bed Filters ____________________________________________________________ 64In Pond Filters _________________________________________________________________ 64Closed Biofilters (close or pressurized systems) ______________________________________ 65Floating Bead Biofilter __________________________________________________________ 65Sinking Media Biofilter __________________________________________________________ 65Combination Biofilters __________________________________________________________ 65

Biofilter Size ____________________________________________________________ 65

Surface Area

Projected and Total __________________________________________ 66Projected or Cross-sectional Area of the Individual Chambers ___________________________ 66Projected or Cross-sectional Area of the Complete Biofilter ____________________________ 66Total Area of the filter material or media ___________________________________________ 66Effects of different media on flow rates ____________________________________________ 66Contact Time within the Biofilter __________________________________________________ 67Shutting Down Biofilters _________________________________________________________ 67Damaging Biofilters _____________________________________________________________ 67

CHAPTER 9: FILTRATION & BIOCONVERSION METHODS _____________________ 68

Alternative Filtration and Bioconversion Methods _____________________________ 68

Ion Exchange - Zeolite ___________________________________________________________ 68

Zeolite and Salt ________________________________________________________________ 68Zeolite as a Biological Filter Medium _______________________________________________ 69Activated carbon _______________________________________________________________ 69UV Lights or UV Sterilizers _______________________________________________________ 69Vegetable Filters _______________________________________________________________ 70Streams as Filters ______________________________________________________________ 70Foam Fractionation _____________________________________________________________ 70

CHAPTER 10: MAINTAINING BIOFILTERS AND FILTERS _______________________ 72

Cleaning Ponds & Filters __________________________________________________ 72

Backwashing Biofilters and Filters _________________________________________________ 73Primary Design Features for Successfully Cleaning Filters ______________________________ 73

Cleaning and Damage ___________________________________________________________ 73Air Blowers ___________________________________________________________________ 74How Often Should Filters Be Cleaned? _____________________________________________ 74


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Water Changes ________________________________________________________________ 75Chlorine and Chloramines _______________________________________________________ 75Fresh Water Caution ____________________________________________________________ 76

CHAPTER 11: EFFECTS OF CHEMICALS & MEDICATIONS ON FILTERS ____________ 77

Effects of Various Chemicals and Medications on Filters & Biofilters _______________ 77

The Koi _______________________________________________________________________ 77Filters ________________________________________________________________________ 77Biofilters _____________________________________________________________________ 77The Pond _____________________________________________________________________ 77

CHAPTER 12: POND-SIDE ANALYSIS OF FILTRATION PROBLEMS _______________ 78

Analysing Pond & Filtration Problems _______________________________________ 78

REFERENCES & ACKNOWLEDGEMENTS ___________________________________ 79

INDEX _____________________________________________________________ 80


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AUTHORS SYNOPSIS

"Koi keeping is a peculiar mix of hobby, art, science, and commerce"

(Professor Dominique P. Bureau of the University of Guelph)

Filtration on Koi ponds can be a somewhat controversial subject often full

of emotion. There are, however, basic principles that apply to all

variations of the filter systems hobbyists may encounter. There are basic

principles to water keeping that apply to all ponds. By adhering to these

basic principles we will successfully maintain the healthy water

environment our koi need.

When it comes to making a plan the ingenuity of koi keepers and koi

dealers never ceases to amaze me. Various things have been successfully

adapted from other applications for use on Koi ponds. It is often in this

adaptation that certain water quality parameters applicable to Koi ponds

are overlooked and so some systems do not work properly.Koi Health begins with successful water-keeping and ends with successful

water-keeping. Aquatic life has existed for hundreds of millions of years

on this planet. Under aquatic conditions that can be considered "normal

and healthy, Koi should live a long, healthy life, free from disease.

We should therefore, strive to replicate nature in our ponds in terms of a

healthy water environment. A healthy pond environment is critical to the

long term survival of Koi and it is not that difficult for the average Koi

keeper to achieve.

Becoming a successful water keeper and then becoming a successful Koi

keeper is far easier for the average hobbyist if they have a clearunderstanding of Koi pond filtration.

The terms filter and biofilter will be used to describe the devices that

remove solid particles and dissolved impurities (ammonia), respectively,

from pond water.

A wide variety of filters and biofilters are available to the koi hobbyist.

Many of these have been adapted and modified from existing

commercially available aquaculture and water processing equipment. Koi

hobbyists must look past advertising claims, past personal points of view

and past system complexity to get a broad understanding of pond

filtration.

It is a fact that all filters and biofilters work. It is when the human

element transgresses certain natural laws of limitation, that failure of the

system results.

Bioconversion is a simple and natural process in nature. Nature works

its as simple as that. The number of living organisms (Koi stocking

densities) that can be successfully accommodated in a limited volume of

water (the pond) is determined by the amount of dissolved oxygen and

the ability of the filtration system to remove toxic wastes from the water.

Our ponds are a closed system and have a limited volume of water. In

order to successfully maintain a healthy environment for our Koi, we haveto clean and re-cycle the same water.


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The filter system has to remove the toxic waste (ammonia) from the

water as fast as it is produced. The filter must also remove solids and

organics (e.g., algae) as fast as they are produced in the pond. We simply

have to add oxygen at a faster rate than it is removed. The purified water

must return to the pond as fast as possible.

This filtration module does not promote a specific biofilter or filter

design idea above any other. All filter concepts are discussed as there

are many solutions to the problems Koi keepers face.

This Module is viewed as a dynamic lecture. New facts and ideas are

continually emerging. As new information becomes available it will be

incorporated into this module.

A perfect pond can be described as one in which the fish are alive and

healthy for some time, the pond is truly clear and the pond does not leak.

The rest is robust debate at the edge of the pond on how to achieve this.

Chris Neaves - 2010


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A COMPARATIVE INTRODUCTION

Imagine a river..

There is a constant inflow of fresh water from far away where there is

plenty of rain. There are waterfalls tumbling over rocks introducing

oxygen into the water. The input = fresh (free of toxic substances) water

with a constant input of oxygen.

There are a host of life forms growing in the water from microscopic

organisms to macro organisms to larger animals such as fish. There is an

abundance of food and although the animal life forms remove oxygen

whilst breathing this is continually replaced. Further any excretion of

ammonia (for example) is diluted by the influx of fresh water as well as

bacterial activity found on the floor and sides of the river. There are a

limited number of fish relative to the amount of fresh water.

Now imagine you have cut a piece of this river out and placed this bit of

paradise in your garden.

What are the consequences of your action ?


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Consequences of your Actions

You have a pond, you add Koi. The life forms in the pond will need oxygen

immediately. This in turn leads to metabolic activity. Food will have to be

supplied and the by-product of metabolism & food is ammonia. Ammonia

is toxic in minute quantities and will have to be removed as soon as

possible.

You remove impurities and add oxygen by moving the water through

pipes to a filtration/bioconversion system and back to the pond.

Thats the basics ofKoi pond filtration now comes the interesting

partgetting it right and this is the art of Koi pond filtration.

Unlimited fesh water

Oxygen added continuously

Limited number of fish and otherorganisms

Unlimited food source

Limited fresh water - what is availablein the pond

Limited oxygen supply

Large number of fish

No Food source

Your piece of paradise

River

Pond

Picture courtesy of National Geographic

Your piece of paradise +

a filter system


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THE ART OF POND FILTRATION

Picture courtesy of National Geographic

Pond filtration is remarkably simple. It is not difficult to imagine the pond,

the piping, the filters, the biofilter and returning the water to the pond

being compared to the human body.

Our lungs introduce air (oxygen) to our system and cells making gaseous

exchange possible. The oxygen allows chemical processes to occur in the

cells. The liver is a filter removing toxins and impurities from the blood.

The kidneys, colon and skin excrete harmful by-products to waste.

There is one golden thread that enables all the functions to work the

circulation of fluids / blood within the body. These fluids carry a host of

vital substances from oxygen to white and red blood cells to hormones to

cell waste products such as carbon dioxide to nutrition etc.

No matter how large and strong the heart is (or a pump on a pond) it is

useless unless the veins and arteries (pipes) are free of restrictions andopen for the circulation of blood (water). The blood that carries nutrition

and oxygen into the cells also carries waste products away. Within the

blood, a host of cells circulate to assist with the immune system, the

nutrition and the oxygenation of the body cells.

It is an effective circulation system that ensures the health of the

organism. It is an effective circulation system that will ensure the health

of your pond and ultimately the health of your Koi.

A failure of any one of several organs could result in the death of the

whole organism. Liver failure will result in the body being unable to filter

and remove impurities from the bloodstream. The body will then die.With kidney or bowel failure the same thing - impurities in the body will

reach toxic levels within a remarkably short time and the organism will

die. A healthy circulation system with strong heart, open veins and open

arteries, is the key to a healthy body.

The volume of water in the pond is the total living environment for our

fish. The pond water is piped (analogous to the blood vessels) to a pump

(the heart) and through various filters (equated to the liver, kidneys etc.

of the body) for purification and rejuvenation. The pond water is brought

into contact with the atmosphere via waterfalls, streams, air stones with

air blowers and/or venturies where oxygen is dissolved into the water

and unwanted gasses are released or de-gassed into the atmosphere just

like the lungs.


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Failure of any one of these systems will result in the death of the pond.

When the pond dies, the fish will die.

The purpose of any filtration on a Koi pond is to remove unwanted

substances from the water continuously and quickly. Just as removing

the sugar and the tea leaves from a cup of tea would need two different

approaches, so too in a Koi pond different approaches are needed fordifferent problems.

Impurities that are dissolved in the water need chemical removal by

bacterial action (bioconversion) or with charcoal or zeolite. Impurities in

the form of solids need mechanical removal (filtration).

A biofilter is a remarkably simple concept. This involves providing enough

area where there is enough space (surface area) for naturally occurring

bacteria to grow on and in sufficient numbers. These beneficial bacteria

the nitrifying bacteria - do a vital job in the pond by chemically changing

toxic fish waste, in the presence of oxygen, to less toxic substances. Its as

easy as that.

Fascinatingly the biofilter is not only home to nitrifying bacteria but home

to countless other varieties of bacteria, fungi and micro organisms. This

incredible diversity of microscopic life works in synergy and plays a vital

role in the success of your pond.

Losses caused by restrictions in unhealthy veins and arteries in the body

compromise the circulation and the health of the person. Exactly the

same occurs in a pond. Piping that is clogged or piping that is too small or

even piping with numerous bends will restrict and reduce the flow rate,

no matter how large the pump. These losses can be substantial to the

point of compromising the design of the system.

Starting at the BeginningView the entire pond system with the piping, the pumps, the various

aspects of the filtration system and the returns as a circle. Where do we

begin within the circle? After all, a circle has no starting point and no end.

The entire pond/water/filtration system must be viewed as one

environment.

Before the fish can be introduced into a pond, before bacterial growth

will occur, before life in the water will flourish, there has to be oxygen

present. As Koi keepers our responsibility is to introduce oxygen into the

system as the starting point. Once oxygen is in the water it must be

circulated throughout every part of the system. Just as in the body, the

oxygen in the blood supply is circulated to every cell. Should the oxygen

supply be cut off from any part of the complete pond system for long

enough, that area will die.

High oxygen levels in Koi ponds are a key element for good Koi keeping.

In order to introduce oxygen into the pond water, the water must flow - it

must move. Once the water is flowing through the system and around

the pond, oxygen will be introduced with the natural exchange of gasses

when the water comes into contact with the atmosphere and the system

will become active and alive.


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The only way oxygen can be dissolved into the water is through

contact with the atmosphere.

Once the system is active and free of chlorine and chloramines, fish can

be introduced. As soon as the fish are introduced they will begin to

excrete impurities into the water as a natural part of metabolism. The

combination of oxygen and excretion from the fish results in the growth

of naturally occurring nitrifying bacteria. These bacteria will grow on all

surfaces within the pond. There they begin their job of using the

ammonia as a food source and convert the fish impurities to less toxic

substances. Bacteria take time to reach large enough numbers to convert

all the ammonia to nitrite and, at a later stage, to nitrate.

It is as easy as that.

It is also a fact that ponds generate enormous amounts of organic matter

in the form of algae. Various other pollutants such as leaves, dust and

debris,contribute to the build-up of unwanted substances in the pond.

The organic matter ends up in the filter system and must be removed

regularly to ensure a healthy environment. Organics not removed from

the pond biodegrade. This process uses oxygen therefore, the available

oxygen levels are reduced and there is competition with our Koi for the

critical oxygen. The by-product of rotting organic material is ammonia so

the ammonia levels rise. You can have a pond with no Koi, low levels of

dissolved oxygen and a high ammonia level!

Any area with large amounts of organic material build-up will have layers

forming. The deeper layers will be cut off from the passing oxygen in the

water and become anaerobic. A by-product of anaerobic bacteria ishydrogen sulphide which is highly toxic to Koi even in minute quantities.

The maintenance of a pond system is absolutely critical to the long-

term health of the fish.

Arm yourself with knowledge and always keep to the KISS principle

Keep It Simple Stupid


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DYNAMICS OF A FISH POND

Water is a very remarkable substance. The extraordinary properties of

water have a direct bearing and influence on the daily existence of our

fish. A fishs body is composed of more or less 80% water. So it is easy toenvisage fish as a volume of water separated from a volume of water (the

pond) by a thin membrane (the skin). The most insignificant changes in

the pond environment will therefore, have a direct and instantaneous

influence on the life of our fish.

Each and every one of these Influencing Factors, lets call them IFs, is

dynamic. This is very important to remember when dealing with pond

situations. Sometimes we can create problems that are not really there

by viewing various parameters in isolation. During the course of a 24 hour

day, each IF (Influencing Factor) has a natural dynamic change. These

dynamic variations can be recorded and a daily pulse or oscillation can be

observed. As the seasons change, so do some of the parameters - the

most obvious is temperature. A pond or water system has a natural bio-

rhythm of life to which fish have adapted to during the course of their

evolution.

At any point in time during the day or year, a measurement of one or

more of the IFs can be different when compared to another

measurement taken at a different time of the day or year. These

fluctuations or dynamics should never be viewed in isolation. A single

reading with a test kit will present an incomplete view of what is actually

going on in your pond. Therefore, you may be panicking and trying to

make adjustments for nothing.

Nitrifying Bacteria

The nitrifying bacteria found in the places we encourage them to grow

(i.e., the biofilters or any wet surface in our Koi ponds, for that matter)

move through a dynamic range of abilities.

As they grow in the biofilters and on all the parts of the pond, they

become stronger. Their collective ability to convert ammonia to nitrite

then nitrate increases as their populations increase, fuelled by an

adequate food source and agood supply of oxygen.

As temperatures drop in the winter months, (below about 50F / 10C),

these bacteria do not die off but become dormant. In periods when their

food supply is reduced they also become dormant. When the Koi

population is increased and / or the feed to the existing fish population is

increased, the ammonia in the water increases. With the increase in the

food supply (ammonia) the population of bacteria will increase, provided

sufficient surface area (usually in the biofilter) and oxygen are available.

As these factors vary, so do the nitrifying bacteria populations. The

nitrifying bacteria are dynamic and ever adapting in the pond situation.

pH

In the morning the pH will be lower compared to a test done in the lateafternoon. The buffering capacity of the water will play a major role in


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the fluctuation of pH during the course of a day. The pH you record is

unique to your pond. Don't be influenced by "perfect situations". Your

pond may be slightly alkaline with a pH of around 7.8 - 8.2. It may be that

your particular pond has a pH range of 7.2 - 7.6. Or there may even be

greater fluctuations. This is the natural, daily, pH cycle of your pond. I

strongly advise against attempting to adjust the pH to a perceived perfectfigure of say 7.2.

When measuring the pH in the late afternoon, you will inevitably find it is

on the high (alkaline) side. The addition of acid to pond water to lower

the high pH can be disastrous at this point in time. The acid will lower

the pH and so will the natural pond cycle during the night. The result

could be - a pH crash.

Sudden substantial fluctuations in pH values will stress Koi and possibly

kill them. Fish do not tolerate sudden substantial changes in water quality

very well. If they do not die outright, the stress they suffer may become a

contributing factor to a lowered resistance to pathogens and a possibledisease, infestation or infection. Measuring pH should be done in

conjunction with measuring alkalinity. The alkalinity will give you an

indication as to the buffering capacity of the water against pH variations.

The amount of algae in the pond (mostly free floating, single cell algae

that makes the pond water green) can have a dramatic effect on pH,

raising it to very high levels in the evening after a full day of

photosynthesis. The opposite effect is observed by a lowering of the pH

in the early morning after a full night of respiration.

Not only the Koi but also the toxicity of ammonia as well as the bacteria

in the filter are affected by pH. Ammonia toxicity increases as pH

increases. The nitrifying bacteria have a pH range that they can survive in.

If your pH fluctuates through a narrow range, your water is well buffered.

Should there be large fluctuations you may need to buffer the water. The

pH of your pond should not rise much above 8.5 at its maximum reading.

Koi have adapted the ability to survive in a pH range of 6.5 - 9. However,

the fluctuation within this pH range should not be large and the pH

change cannot be sudden.

Temperature

On most occasions temperature will be lowest in the morning just before

sunrise and the highest at sunset, (unless your pond is built on a nuclearwaste dump, which generates its own heat). Temperature is influenced

by the amount of sun, the intensity of the sun the pond receives and

other factors such as the wind speed during the day or night. Evaporation

cools the water. Generally speaking, Koi should not be subjected to more

than a 5C (9F) change in water temperature over a 24 hour period and

the change should not be sudden. Always adjust the temperature

gradually when moving Koi around. An upward movement is tolerated

better than a downward movement in temperature. Most ponds will

have a 1 - 3C (1.8 - 5.4F) variation in temperature in a 24 hour day /

night cycle. Koi are more affected by temperature variations at lower

water temperatures. And, you will notice Koi are more affected by asudden lowering of water temperature than a sudden rising of water

temperature.


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Certain areas in the country can experience a 10 - 15 C (18 - 27F)

atmospheric drop in temperature in a day when low temperatures are

accompanied by high winds. The temperature in a smaller volume pond

can drop significantly under these circumstances. The Koi will suffer from

stress and disease problems can occur later.

Oxygen

Oxygen is possibly the single most important element in pond water - and

the most neglected aspect of Koi keeping. For life to exist in water there

must be oxygen dissolved in it. The fish, the bio-filter, organic

decomposition, etc., all extract oxygen from the system. Oxygen is

introduced into the water through gaseous exchange between the

atmosphere and water molecules. Oxygen is introduced into the pond via

contact with the atmosphere through design considerations such as

streams, waterfalls and apparatuses such as venturies and air blowers.

High turnover rates will promote higher oxygen levels. Photosynthesis by

algae during the day introduces additional oxygen, but removes it atnight. Air under pressure through venturies can cause gas imbalances in

the water and need careful consideration as to their placement in the

pond.

Oxygen levels can fluctuate dramatically during the day and night as well

as during periods of high and low temperature. There can be significant

oxygen variations in ponds with poor circulation or in ponds which do not

move the water away from the bottom of the pond, i.e., the point

furthermost from the atmosphere. There is less oxygen in pond water at

higher altitudes (6000 ft / 1600 m above sea level) - about 18 - 20% less

than at the coast (sea level). There is continual competition in the pond

for the limited amount of oxygen available at any given time. The fish, theplants, the micro organisms all need oxygen rich water - all the time.

Algae and submerged plants have a dramatic influence on oxygen levels

in a pond during a 24 hour day / night cycle. The photosynthesis process

during sunlight may rocket oxygen levels to saturation point and beyond.

However, a dramatic plunge in oxygen with the reversal of the

photosynthesis process (respiration) at night can spell disaster, even to

the point of fish suffocating in ponds at dawn.

It has been found that if the oxygen levels are 25% below optimum levels

first thing in the morning, growth rates are reduced. The turn-over rate

will have a direct bearing on oxygen levels as will the stocking densities offish. The faster the turnover rate the more water will come into contact

with the atmosphere and the more gaseous exchange will take place. The

more fish there are in the pond, the less oxygen there is in the water as

they are all respiring, all the time.

Higher water temperatures in summer mean there is less oxygen that can

be dissolved into the water. Higher water temperatures result in faster

metabolism, which in turn means that the oxygen dissolved in the water

is needed in greater quantities by the fish and other life forms when the

water is able to hold less dissolved oxygen due to the higher

temperature. A shortage of oxygen will be noticed by observing the Koi

collection first thing in the morning. If the Koi are moving lethargicallyand hovering near the surface you may well have an oxygen deficiency.

Oxygen shortages have been measured in ponds with fancy pumps and


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filters - but with a lack of adequately exposing the water molecules to the

atmosphere. A shortage of oxygen can also be observed by watching the

respiration of the fish. If the fish are respiring heavily, or "piping", they

could be, stressed, have a gill problem, the pond water could be low in

oxygen or, the fish could be exhausted for some reason.

Ammonia

The levels of ammonia andtoxicity of ammonia are never constant. A few

hours after feeding the ammonia level will rise as the nitrogen wastes of

the fish are excreted. This can actually be measured. A measurement just

before feeding should produce the lowest or no ammonia reading (if

everything is working). However, an hour or two after feeding a high

ammonia level will be recorded as the fish are now excreting their

metabolic waste products. Interestingly, a corresponding drop in oxygen

levels at this time has also been measured in ponds as the Koi consume

more oxygen for the metabolism of the food.

The higher the temperature, the faster the metabolic rate and the

quicker ammonia will be released into the surrounding water. However,

there is another dynamic related to ammonia - the toxicity of ammonia

(NH3) is not constant during the course of a single day. Ammonia is found

in two forms in the pond. The toxicity of ammonia is pH dependant.

Ammonia changes from ammonia to ammonium (NH4+) as pH drops, i.e.,

it becomes less toxic. As pH rises (naturally during the day) the

ammonium (or a percentage of the ammonium) converts back to toxic

ammonia.

Whilst very high pH, above 9, makes a higher percentage of ammonia

more toxic and has certain negative effects on Koi, low pH has othereffects on the pond system. The bacteria in the biofilter are oxygen and

pH dependent. The nitrifying bacteria that oxidise ammonia to nitrite

have an optimum pH range of 7.8 - 8.5. The lower limit for the reasonable

growth of nitrifying bacteria is given as a pH of 7.0 - 7.6. The upper limit is

a pH of 9.4. Around pH 6.5 nitrifying bacteria virtually cease to function.So what now?

Into this dynamicpond system we introduce two critical factors - fish and

man. How can our Koi possibly survive in an environment that can

become 100 - 200 times more alkaline / acidic, have a temperature

change of more than 40F (5C), have oxygen levels that can drop and

rise dramatically, and have a shifting ammonia / ammonium percentage

in a single day? How can our fish possibly survive the bombardment of

toxic chemicals that are added to the pond in the name of medications?

The average enthusiast does not have the money to spend on equipment

to monitor the water continuously. How can they possibly monitor all

these IFs (Influencing Factors) continuously and make daily adjustments

in order to provide the perfect environment for their Koi?

The answer is simple - if your Koi are alive and healthy and growing well -

you are doing it right. Your Koi are the best test kits you have. It may be a

joke amongst Koi collectors that when a new pond is built they always

suggest placing a few "testers" into the new pond to "test" the water. A


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joke yes - but it is an excellent way of testing the water for your new

arrivals and new pond system.

The ancestors of Koi, the common carp, have been living successfully in

freshwater rivers for millions of years. There are ancient fossilised

remains of the ancestors of carp.

It is a scientific fact that whilst a pH of 7 - 7.5 is advocated as "ideal" for

keeping Koi, they will live comfortably in a pH range of 6.5 - 8.5. A

temperature range of 22C - 28C (72F to 82F) is ideal for keeping Koi,

however, they winter well down to 10C (50F) and, provided the

temperature is not below 8C (46F) for too long a period of time, they

suffer no adverse affects after winter. Some reports give the lower

temperature limit for winter survival as 35F. The critical factor is that

these fluctuations must be gradual. Actually, the less often or more

gradual the temperature fluctuates, the less stressful the environment

will be.

Oxygen levels are maintained by circulating the water correctly in thepond and by bringing the water into contact with the atmosphere

continuously. The faster the turn-over rate of the whole system, the

higher the oxygen level will be in the pond.

Ammonia levels can be controlled successfully by providing adequate

surface area for bacterial growth. Additional surface area is provided by

the media housed in the biofilter. The high oxygen levels provided by high

turn-over rates will activate the bacteria and the metabolism of the fish.

The natural immune system and osmoregulation of the fishs body has

adapted over millions of years to counteract natural fluctuations in the

water and attacks from the outside world. Provided the fluctuations arenot too great or too sudden, the fish has the ability to adjust and survive

the daily, monthly and annual bio-rhythms of the pond.

Stocking Densities

Quick Info

Stocking densities have a direct influence on the overall health of your Koi

and the quality of the pond environment.

Heavily stocked ponds have a higher chance of disease outbreaks.

Heavily stocked ponds are stressful to Koi.

The higher the stocking densities the faster you have to remove the

impurities and the faster the clean water should be returned to the pond.

As Koi grow they take up much more space, consume much more oxygen

and add much more ammonia to the system.

Facts You Must Know

Every time a Koi doubles in length it has about 8 times more body mass.

This has severe implications on your pond and filtration system.

8 times the body mass = 8 times more oxygen consumed + 8 times moreammonia added to the pond.


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Higher stocking densities run a greater risk of the collection suffocating in

the event of the pump being off for some time.

Decision Time

After a year or two, if your Koi have doubled in length, it may be decision

time

8 times

the bodymass

8 timestheoxygenremoved

8 timestheammoniaadded

Every time a single Koi doubles in length

Less KoiMore filtration and a faster

turnover rate or possibly

larger filters


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Koi Length to Mass Ratio

The larger the mass of a Koi, the greater the oxygenconsumption, the greater the amount of ammonia excreted intothe water.

Weight increases disproportionably with body length. A doubling in body length does not produce a doubling in mass. Note the 7 - 8 fold mass increase as the length doubles from

20cm to 40cm.

Each Koi can double in length in about two years. This wouldmean a 7 - 8 fold increase in the load on the biofilter and the

oxygen demand. - plan ahead -

The Effects of Koi Growth on the Pond System

Would you have originally stocked your pond with 640 x 10 cm Koi?

40 cm koi

These same 10 koi grow to 40 cm the koi keeper now has the equivalent of640 x 10 cm koi in the same pond - with the same filtration etc

20 cm koi

When these 10 x 10 cm koi have doubled in length to 20 cm there is theequivalent of 80 x 10 cm koi in the pond.

10 cm Koi

10 x 10cm koi in a pond to begin with

0

500

1000

1500

2000

10cm 20cm 30cm 40cm 50cm

Length of Koi in cm

Estimated Mass in

grams


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CHAPTER 1: DEFINITIONS

AS THEY RELATE TO KOI POND FILTRATION

AC TI V A TED SL U D GE

Process where nutrients are kept suspended in the water by pumping or

more commonly aeration. A mixture of free floating bacteria and algae

utilise and convert the nutrients through processes such as nitrification

and photosynthesis.

AEROBICLiving or occurring in the presence of oxygen. For example aerobic

bacteria, require oxygen to live. The opposite of aerobic is anaerobic.

AIR LI FT

Air lift is a contained column of bubbles and water used to provide a

vertical flow or current. The air lift uses a bubble source, usually some

sort of diffuser, to supply bubbles to the bottom of a column which is

often a pipe or similar containment device. As the bubbles mix with the

water, they create a mix which is less dense than water alone. Gravity

then has less effect on the water in the contained column and this water

rises higher than the more dense water on the outside of the column.An opening at the top of the column allows the water/air mixture to

escape. The head and amount of water that an air lift can pump is a

function of the ratio of air to water, the amount of air pumped in, the

depth of the diffuser, the ratio of the submerged part of the column to

the part of the column that protrudes form the water and the diameter of

the pipe.

AM B I EN TAMMONIA

Ambient ammonia is the background level of ammonia in the pond water

and will likely vary over the course of a day. There can never be zero

ammonia in the pond as the Koi are continuously excreting ammonia inthe pond whilst the biofilter is continuously removing the ammonia from

the water.

AMMONIA

Ammonia is toxic to fish in minute quantities. It is the unionised form of

ammonia, (NH3), that is the toxic form, although sometimes the term

ammonia is used to express the total ammonia (i.e., unionised and

ionised).

The amount of ammonia produced by the fish is approximately 0.03 x

feed. Therefore for every 1000g of high protein feed that is fed, about

30g of total ammonia is produced. This is excreted by the fish in the urineand from the gills. The ammonia production will vary throughout the day
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with the 0.03 x feed value being the average. In ponds where koi are fed a

few large feedings per day, the maximum ammonia production at any

time may be twice this amount with corresponding periods of very low

ammonia output.

BACK FL U S H I N G/BACK WASHING

Back flushing is the general term used to describe the process where

filters are cleaned. It is also called back-washing. It is usually achieved by

the flow in the filters being reversed and the water used to flush being

discharged to waste.

BAFFLE

A device, such as a plate or screen, installed to alter / reduce the velocity

of water.

BI O FI L TER/BIO-CONVERTER

A biofilter is a specialized or dedicated area of the pond system designed

to provide the proper environment for large colonies of beneficialbacterial (nitrifying bacteria, chemolithotrophs and heterotrophs) to

grow. These dedicated areas are referred to as biological filters, biofilters

or bio-converters.

BI O L O GI C A L FI L TRA TI O N

Biological filtration is the process of converting ammonia, through

oxidation or reduction, in the presence of oxygen, to less toxic nitrite and

then nitrate. The ammonia is converted to nitrite by a group of bacteria

called nitrosomonas. The nitrite is converted to relatively harmless nitrate

by a group of bacteria called nitrospira. The level of ammonia in the pond

is used as one indicator that biofiltration is taking place. Should the nitritelevel be zero, this would be an indication that full bioconversion is taking

place.

Another type of biological filtration which is sometimes used in

aquaculture, especially in high rate re-circulation systems, is de-

nitrification. De-nitrification filters convert nitrate to nitrogen gas. The

bacteria responsible for this conversion are anaerobic.

BOD

Biochemical oxygen demand, or BOD, is the amount of dissolved oxygen

needed by all of the aerobic biological organisms in the entire pond

system. This includes the oxygen needs of the fish, the bio-filter and theplants, (at night), as well as the oxygen needed to biodegrade the organic

waste such as fish faeces and plant material.

C ANISTER FILTER

Enclosed housing usually containing a fine mesh basket, into which

filtration or other media can be put. Canister filters are often used to

house activated carbon or zeolite. Generally they are small and are

designed for low flow rates, although larger units are sometimes custom

built.

CARBON D I O X I D E

Carbon dioxide is produced as a result of respiration by fish and other

aerobic organisms such as plants. The amount of carbon dioxide
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produced is directly proportionate to the oxygen consumed. For every 1g

of oxygen that is consumed, 1.4g of carbon dioxide is produced.

Carbon dioxide has the effect of increasing the acidity of the water. It is

present in three different forms; CO2 (free carbon dioxide, which is the

toxic form), HCO3- (bicarbonate ion), and CO3-- (carbonate ion). The

concentration of each is dependent on the pH of the water.

Good oxygenation of Koi ponds will control and eliminate carbon dioxide.

CARRYINGCAPACITY

Carrying capacity is the amount (either expressed in weight or number) of

Koi that a given system is capable of supporting. (see stocking densities).

CARTRIDGEFI L TERS

Cartridge filters are enclosed vessels which house a replaceable filter

membrane. The filter membrane is generally of a pleated or a woven

material. Cartridge filters are used primarily for the filtration of particles

20 microns and smaller in size, i.e., very fine filtration and not always

practical on Koi ponds.

CH A M B ER

An area or enclosure where media is housed or settlement takes place.

CH EM I C A L FI L TER

Zeolite and Activated Carbon are geological materials that will adsorb

ammonia and other substances directly from the pond water.

DE-GASSING

A process which removes undesirable gasses or undesirable gas levels,e.g., supersaturated gasses.

The main function of a de-gasser is to create a large interface between

the water and the atmosphere. Waterfalls, streams or heavy aeration via

diffusers increase the interface between the atmosphere and the water.

These are the de-gassers of the Koi pond.

DE- N I TRI FI C A TI O N

De-nitrification is the process where bacteria convert nitrate into

nitrogen gas. The de-nitrification process is an anaerobic process and

requires a carbon source for the bacteria to perform their task properly.

DEN I TRI FYI N GBACTERIA

De-nitrifying bacteria are free-living bacteria that convert nitrates to

gaseous nitrogen and nitrous oxide. These are anaerobic bacteria. Their

cellular respiration occurs in the absence of oxygen.

DI S S O L V ED O X YGEN

Dissolved oxygen is the oxygen gas which is dissolved in water (i.e.,

oxygen that is attached to the water molecule not that which is present in

bubbles).

DI S S O L V ED SO L I D S

Dissolved Solids or Total Dissolved Solids (TDS) is a measure of the

combined content of all inorganic and organic substances in a body of
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water in a molecular, ionized or micro-granular (colloidal) suspended

form.

Many people define Total Dissolved Solids as solids that must be small

enough to survive filtration through a sieve the size of two micrometers.

The amount of TDS present in the water affects its clarity.

FI L TER

A physical process (i.e. one not reliant on chemicals or biological

organisms) designed to separate/remove solid particles from water.

FI L TERS I N PARALLEL

When the water to the filter chambers is divided into two or more

portions and each portion travels through only one of the filter chambers,

the filter chambers are said to be in parallel.

FI L TERS I N SEQ U EN C E/SERI ES

When the water moves from the first chamber or container to the secondchamber to the third chamber etc., the filters are in sequence or series.

FL OW RATE

Flow rate is critical for the pond as it determines the rate at which

excretory products such as faeces, carbon dioxide and ammonia are

removed from the pond and brought into the filtration system for

purification i.e. removal from the system.

FL OW RATE& SP EC I FI C FL OW RATE

Flow rate is the volume of water that flows past a given plane or through

a filter system in chamber of a given surface area over a given length of

time. It is usually expressed in terms of volume/time, (e.g. Gallons per

Minute (GPM) or Litres per Minute (LPM).

Specific flow rate is the flow rate divided by the projected area across

which the flow takes place and is given in: volume/time/area. If the

specific length, units of volume and area are the same, e.g., feet as in

cubic feet and square feet or cubic meters or square meters, it can be an

expression of velocity, but only if no media is involved (water only).

FOAM FRA C TI O N A TO R

A narrow device with a rising column of air bubbles and a descending

volume of water. A foam fractionator is used to remove DOC (dissolved

organic carbon or scum) from the pond water.

FRI C TI O N LOS S

Friction loss is the reduction in velocity and pressure of water flowing

through a pipe caused by the drag effect from the inner surface of the

pipe. The more rough and more profiled (shaped) the surface, the greater

the friction loss it imposes. The calculation of friction loss is important,

when designing systems, to ensure that a pipe is large enough for

sufficient water to flow through it. Friction loss is also sometimes called

head-loss or pressure loss, as it has the effect of reducing the amount of

head (or pressure) of the water.
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GAS BU B B L EDI S EA S E

Gas bubble disease is caused when supersaturated gases in the water are

absorbed from the water into the body fluids of the fish. Gasses in

supersaturated water will try to escape from the water into any medium

where the gas saturation level is lower (e.g., into the air, or in the case of

gas bubble disease, into the blood and other fluids of the fish). It is mostcommonly seen in the yolk sacs (of newly hatched fry), gills, eyes and

occasionally the fins as these are the areas of the body which have the

most gas permeable membranes.

The gas then causes bubbles to form inside capillaries and under the skin,

restricting the blood flow causing haemorrhages and clots. Fish often

show signs of swimming upside down or vertically, sometimes looking as

if they are gasping for air at the surface.

HETERO TRO P H I C BACTERIA

Heterotrophic bacteria are a species of bacteria that digest or break down

organic material to obtain their energy. Heterotrophic bacteria grow

alongside the nitrifying bacteria in biofilters.

HYD RA U L I C LOA D

The relationship of flow rate to the available media surface area is called

the hydraulic loadon the media bed. The first objective of hydraulic load

is to encourage the water to move through the filter bed evenly at all

points of contact between the media and the water.

HYD RO GEN SU L P H I D E

Hydrogen sulphide is produced by anaerobic bacteria in anoxic water

(water depleted of dissolved oxygen), silt and mud, especially whereorganic loading is high and in heavily stocked ponds. Hydrogen sulphide

exists in two forms in the water, HS-

(ionised sulphide ion) and H2S

(unionised, hydrogen sulphide). Hydrogen sulphide (the H2S form) is

highly toxic to fish.

In well oxygenated water, hydrogen sulphide is rapidly oxidised to

sulphate. The best way to stop hydrogen sulphide from being formed is

to maintain a clean, well oxygenated and mixed system with no layering

of the pond water.

Most fish species are extremely sensitive to hydrogen sulphide gas.

As low a concentration as 0.002 mg/l can have a sub-lethal effect, causing

prolonged stress and gill damage. A level of 0.01 - 5.3 mg/l is lethal.

IO N EX C H A N GE

Ion exchange is the exchange ofions from one medium, (the pond water),

to another medium, (usually a solid such as zeolite). There are two types

of ion exchange material, anionic and cationic. The former will exchange

positive ions (as it has negative ions built into its structure) and the latter

will exchange negative ions (as it has positive ions built into its structure).

The most commonly used ion exchange in aquaculture is with the use of

zeolite in which positive ions are held within a silicate lattice.
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LO GA RI TH M I C SC A L E

A logarithmic scale is one which increases in real terms by a factor of 10,

for every increase in the scale of 1. For example a logarithmic scale of 1,

2, 3, 4, 5, in fact represents values of 1, 10, 100, 1000, 10000.

An example of a logarithmic scale is the pH scale, where an increase of 1represents a 10 fold rise in real terms, so a rise of 2.0 in pH (e.g. from 6.0

- 8.0) actually means a 100 fold increase.

MECHANICAL FI L TER

Mechanical Filters will be referred to as filters. These are areas where

suspended and settled solids are collected or trapped for removal from

the pond system.

MECHANICAL FI L TRA TI O N

Term used to describe a physical process (i.e., one not reliant on

chemicals or biological organisms) to remove solid particles from the

water.

MEDIA

Media is any substrate used to support living organisms, (e.g., contained

in a bio-filter), and / or any substrate used to filter solid material from the

water.

NI TRA TE

Chemical symbol NO3 - Nitrate is formed as a result of the breakdown of

ammonia to nitrite and then to nitrate by nitrifying bacteria. (see

nitrification)

Nitrate, along with phosphate, form two of the critical elements that all

plants require.

Nitrate is relatively harmless to koi which can tolerate a nitrate level of up

to 200mg/l. However, it is recommended that to maintain pristine water

quality, koi keepers should limit the nitrate level in the pond to 20 mg/l.

For every 1g of ammonia converted to nitrate, 4.57g of nitrate are

produced.

NI TRI FI C A TI O N

Nitrification is the biological oxidation of ammonia by bacteria into nitrite

followed by the oxidation of these nitrites into nitrates.

NI TRI FYI N GBACTERIA

Bacterial species found in nature that oxidise ammonia to nitrite and then

nitrate. These are chemolithotroph species of bacteria that live in an

oxygen rich environment. They utilize mostly inorganic (without carbon)

compounds as their energy source, and require carbon dioxide (CO2) for

their source of carbon.

NI TRI TE

Chemical symbol NO2 Nitrite is the first step in the oxidation of

ammonia by bacteria to nitrate. (see nitrification) When a biofilter has

matured the conversion of ammonia to nitrite and the conversion of

nitrite to nitrate occurs before the water exits the filter. There will
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however be a residual amount of nitrite left in the water that will usually

be converted to nitrate once the water re-enters the biological filter on

the following re-circulating cycle.

The general guide line for a toxic concentration of nitrite is a level above

0.1mg/l.

NI TRO B A C TER

A nitrobacter is a species of aerobic bacteria that converts nitrite to

nitrate in soil. It was originally thought to be one of the critical bacteria in

biological filtration. Later work showed nitrospira to be the species that is

most responsible for conversion of nitrite to nitrate. (see also biological

filtration, nitrification)

NI TRO S P I RA

Nitrospira is the species of aerobic bacteria most responsible for

converting nitrite to nitrate in water.

ORGA N I C S

Organics is the term used when referring to any material that consists of

live or dead cells, or any carbon containing material that is capable of

being broken down by biological means. It is any material containing

carbon that is derived from a life form. Examples algae, leaves, fish

faeces.

OZONE

Ozone (O3) is an unstable molecule, a "free radical" of oxygen which

readily gives up one atom of oxygen providing a powerful oxidizing agent

which is toxic to most waterborne organisms.

SAND FI L TERS

Sand Filters on Koi ponds are an adaptation of pressurised filters for

swimming pools. Modification for use on Koi ponds include coarse gravel

in place of the very fine sand used in swimming pool applications. The

openings in the arms at the bottom are widened slightly to increase flow

rates.

Sand filters can be used for mechanical as well as biological filtration.

Basic pressurised containers can also be adapted for use in fluidised sand

bed filters.

SETTL ED SOLIDS

Settled solids are the non-dissolved pollutants that settle towards the

bottom of the pond, tank or chamber. Some examples of settled solids

are; heavier particles of dust, sand, water logged organic material and

leaves.

One of the prime pollutants, in terms of the water quantity in ponds is

dead algae. Algae accounts for as much as 60 70% of the organic

material found in ponds. However, in some heavily loaded ponds, it may

be as high as 90%of the organic material which clogs up the filter system.

SP EED (O F W A TER FL O W )See velocity
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STO C K I N GDENSITY

The weight or number of Koi held per unit of water volume. The effects of

overstocking can be alleviated to some extent by attention to the water

quality and also the feeding regimes. There is an accumulative effect of

stress on the Koi as stocking densities increase.

STRA TI FI C A TI O N

Stratification is the separation into different "layers" of water by distinct

boundaries. This can relate to thermal layers and/or dissolved oxygen

layers.

The use of simple aeration devices as well as water movement

(circulation) can prevent the occurrence of stratification and guard

against its potentially harmful effects.

SU P ERS A TU RA TI O N

The term given to a body of water that contains more than the "natural"

amount of a particular gas or gases. The sum of all the gasses dissolved inthe water is called the total gas pressure of the water. Under normal

conditions the total gas pressure is 100%. Under some conditions

however, the gas pressure can increase above 100% (super saturation)

and it can then cause problems to fish (such as gas bubble disease). As

nitrogen and oxygen form over 99% of the earth's atmosphere, these are

the gasses that we are primarily concerned with. Nitrogen can cause fish

health problems at anything greater than 100%, whereas oxygen can be

safe up to and over 200%.

When pressurised, by a pump for example, water can hold more than its

capacity under normal atmospheric pressure. This is not a problem unless

there is air being sucked into a pipeline, which then readily dissolves.

When water leaves a pressurised pipe and enters the pond, it is suddenly

returned to normal atmospheric pressure. All the extra gas in the water is

now more than the natural amount that the water can hold and the

water becomes supersaturated.

Oxygen is rarely a problem as the fish have the ability to withstand

supersaturated oxygen concentrations of up to 200%. The fish will

immediately begin to reduce the amount of oxygen in the water.

Nitrogen however can only escape out of the water through contact with

the atmosphere, and a reduction from 110% to 100% can take up to

several hours.

SU S P EN D ED SOLIDS

These are solids that remain in suspension in moving water. The

individual particles are generally invisible to the naked eye. They cannot

pass through a sieve of 1 2 micrometers.

TU RB I D I TY

Turbidity is the cloudiness in pond water. It can be a combination of

several suspended organic and inorganic materials.


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UVLI GH TS

Ultra-Violet Lights are a type of light that has a specific band of

wavelengths primarily used for controlling algae. UV lights are often

referred to as Ultra-Violet clarifiers by manufacturers in the hobby.

Clarifiers, as the name implies, clear the water of algae. This can beaccomplished with 20 - 30 thousand microwatt-seconds per square

centimetre. Many bacteria die out at 15 thousand microwatt-seconds per

square centimetre. If you want to kill off protozoan parasites, you will

need 90 thousand microwatt-seconds per square centimetre or more.

Most people buy these devices to kill algae, i.e., they are using them as

clarifiers.

VEGETA B L EFI L TER

A vegetable filter is an area in the pond system, usually away from the

Koi, where plants are contained and encouraged to grow. The pond water

is run through and over the plants and/or the plants roots in this area

(such as a stream bed). Plant filters are primarily used to remove nitrates

from the water.

VELOCITY

Velocity is the speed at which a fluid travels. In our case the speed at

which the pond water travels through any part of the system.

The velocity or speed of the water is less in a bigger tank than it is in a

smaller tank (given the same flow rate through the tank).

VENTURI

A venturi is a device for adding air under pressure to pond water. As the

water passes through a restriction in a pipe, it forms a vacuum at the end

of the restriction. A hole bored into the pipe at the point where this

vacuum occurs will cause air to be drawn into the flow of water.

VOI D SP A C E

Void space is the open space between the pieces of media in filters.

VO RTEX

A vortex is a mass of water moving in a circular motion, where solid

particles are drawn into the centre. The circular movement of the water

is dependent on the tangent angle of the water entering the chamber or

container.


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CHAPTER 2: OXYGEN

Dissolving Oxygen into the Water

The only way oxygen can dissolve in water is through contact with theatmosphere. This is accomplished by diffusion between molecules of

water in contact with the oxygen in the atmosphere. At the same time as

oxygen is entering into the water, carbon dioxide is released or de-gassed

into the atmosphere.

Some interesting deductions can be made from this fact.

a. All the water's molecules should be brought into contact with the

atmosphere at some time during a complete circulation cycle.

b. The water should ideally be brought into contact with the atmosphere

as much as possible (surface area and turnover rates) to assist with the

diffusion of oxygen into the water and the release of unwanted gasses

into the atmosphere.

If the water was drawn exclusively from the surface of the pond and

returned to its surface, the oxygen levels in the lower levels of the pond

will become critically low. Unless supplemental circulation within the

pond is provided (like air stones) the water will take on a "dead" look.

This statement is difficult to quantify. Experience will guide Koi

enthusiasts to be able to identify water low in oxygen. This is similar to

koi judges gaining experience and being able to appreciate different

shades of white or what is called lustre when judging koi. In areas of low

or no oxygen, anaerobic bacteria will flourish. The settled organics andsolids will decompose and produce deadly Hydrogen Sulphide, gradually

poisoning the system and fish.

Dissolved Oxygen

Dissolved oxygen is critical for the success of the pond and fish. High

levels of dissolved oxygen will ensure good growth, health, lustre and

colour.

The aim is to get and keep dissolved oxygen levels as close to saturation

levels as possible.

Factors Affecting Dissolved Oxygen in Koi Ponds

Koi the larger the individual koi and/or the higher the stocking densities

the more oxygen is consumed and removed from the water.

Decomposing organic matter this removes large amounts of oxygen and

will compete with the koi for the amount of oxygen available in the

water.

Altitude - there is less air pressure at higher altitudes and consequently

less oxygen can be dissolved in the pond water. Ponds at altitudes of

1600m or 6000ft have about 20% less oxygen in the water because of less

atmospheric pressure.


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Temperature temperature governs the metabolic rate of life in the

pond and temperature also affects the amount of oxygen that can be

dissolved into the pond water. The higher the water temperature, the

less dissolved oxygen it can hold.

Dissolved Oxygen and Temperature

Temperature plays a major role in the dynamics of a Koi pond.

Temperature governs the metabolic and growth rate of the fish and other

life forms. Temperature governs the amount of oxygen that can be

dissolved into the water.

The saturation level of oxygen in water decreases as temperature rises.

All forms of life in the pond, from the fish to the bacteria, are constantly

removing oxygen from the water. As temperatures increase so does the

oxygen consumption.

Organic matter such as dead algae and dead bacteria decompose and

place an additional strain on the oxygen supply.

Algae use a vast amount of oxygen at night when the photosynthesis

process is reversed and respiration takes place.

See Turnover Rates and Flow Rates in Chapter 5 for suggestionson how to replace oxygen consumed in pond water.

The following chart demonstrates dissolved oxygen levels at different

temperatures and different altitudes.

Dissolved Oxygen and Temperature Graph

4

5

6

7

8

9

10

11

12

13

14

5C 10C 15C 20C 25C 30C 35C

ppm Mg/L

Pond water

oxygen

saturation at

6000ft/1600m

Pond water

oxygen saturation

at sea level

Temperature in C

Danger levels of low oxygen detrimental to koi health


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Chapter 3: SOLIDS - ORGANIC &

INORGANIC SOLIDS

The chapter on organics and solids is introduced early in this filtrationstudy material for good reason.

Solids in organic and inorganic form are the two main pollutants which

cloud the water and prevent us from seeing our Koi. The cloudiness in Koi

ponds is called turbidity.

If we can identify the sources of organics and solids we can begin to

control them and in this way bring some relief to the filtration system

early on in the battle for clear water.

Filtration starts with the control of organic and inorganic solids.

Pollutants

Pollutants seem to be a catchall word used in Koi keeping for anything

that is not wanted in the Koi pond!

This can range from fertilizer run-off from the garden, insecticide spray,

dust, leaves, grass cuttings, etc.

The various pollutants found in Koi ponds are discussed within this

document.

Inorganic SolidsInorganic solids are introduced into the pond water from atmospheric

dust, run-off from the garden or overhangs (roofs, bridges and pergolas),

the wash-off from trees and the vegetation around the pond as well as

by rain. If you have ducks on your Koi pond you have a problem with

solids in your water. The ducks swim then walk in the garden and in their

food and then swim again bringing large amounts of solids into the pond.

Solids can build up and begin to cloud the water. The mechanical

filtration part of your filtration system is designed to trap and remove (by

flushing the chamber/chambers) solids from the pond.

Suspended Solids

These are solids that remain in suspension in moving water. The

individual particles are generally invisible to the naked eye. Suspended

solids consist of an inorganic fraction (silts, soil, dust, etc.) and an organic

fraction (live and dead algae, zooplankton, bacteria, and detritus). Both

inorganic and organic solids contribute to the turbidity or cloudiness of

the water.

Decomposing organic material consumes large amounts of oxygen and

contributes to the bio-fouling of the water.

Many suspended solids can be trapped in the filter systems but not all.When the fine suspended particles find a place to settle in pockets or

areas of slow moving or stagnant water they become sediments or silts.


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This sediment can increase in depth over time and the deeper layers will

be cut off from the oxygen in the passing water creating anaerobic areas

that will produce toxic hydrogen sulphide.

Larger solids such as leaves will settle out rapidly on the pond floor or in

the bottom drains or in the settlement tanks outside the pond. These

organic materials must be removed regularly from the pond system asthey are biodegrading, adding to the ammonia load and removing oxygen

from the pond water.

Suspended solids can be very fine particles of minerals and dead algae

cells. Because of their very small size they are difficult to remove from

the pond water. Algae cells will not all be trapped in the filters. Most will

pass through back to the pond.

Bentonite clay can be added to the pond water to increase the

flocculation of these fine particles making them easier to filter from the

water. Bentonite is sold as Bentonite or montmorillonite clay. The

Bentonite comes in two forms calcium Bentonite and sodium bentonite.The sodium Bentonite clumps more vigorously than the calcium

Bentonite.

Although Bentonite is found in many clumping cat litters and Koi keepers

are often tempted to use them in ponds, these are best avoided. Cat

litters are in granular form. The granules clump (which is what they are

supposed to do!) and can block bottom drains and piping. Using a

powered Bentonite is far better in Koi ponds. Manufactures of clumping

cat litters often add chemicals to introduce a fragrance to the cat litters.

Some cat litters are sprayed with a plastic compound to reduce the dust

associated with the clay. Other cat litters have colorants added for

commercial appeal. As many of the cat litter additives are not declared, it

is best and safest to avoid clay cat litters in Koi ponds.

Pots with soil and plants inside the Koi pond will be a target for the Koi.

They will love the new roots or plant growth and they will dislodge the

soil. This will become a major source of turbidity. There will be solids that

will settle and fine suspended silts which are difficult to eliminate from

the pond water and can be identified as a brownish colour to the water

as opposed to the greenish colour of algae. Water changes are the best

way to eliminate soil/silt from the pond. A good mechanical filter can also

eliminate this pollution.

Suspended solids can also refer to small solid particles which remain in

suspension as a colloid or possibly due to the motion of the water.

Colloids are very fine particles that are dispersed within the pond water

in a manner that prevents them from being filtered easily or settled

rapidly.

Dissolved Solids

Dissolved Solids or Total Dissolved Solids (TDS) are a measure of the

combined content of all inorganic and organic substances suspended in a

body of water in a molecular, ionized or micro-granular (colloidal) form.

Many people define Total Dissolved Solids as solids that are small enoughto survive filtration through a sieve the size of two micrometers. A

micrometer, also called a micron, is one thousand times smaller than a


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millimetre. It is equal to 1/1,000,000th (or one millionth) of meter. Things

on this scale usually can't be seen with the naked eye.

Most of the dissolved solids are a broad array of chemical contaminants

such as calcium, phosphates, nitrates, sodium, potassium and chloride.

Other harmful total dissolved solids can be pesticides.

Total Dissolved Solids (TDS) are differentiated from Total Suspended

Solids in that the TSS cannot pass through a sieve of two micrometers and

yet are indefinitely suspended in solution.

Organics

Organic pollutants take two major forms in Koi ponds plant matter (in

the form of algae, leaves, grass clippings, flowers, etc.) and fish faeces.

Organics in the form of algae and fish faeces can be the major cause of

turbidity and pollution in our ponds that our filters have to contend with.

The organic load will vary from pond to pond, from region to region and

from season to season.

The success of organic pollution control lies in the design AND

maintenance of the system. (see page 71)

Removing solids is significantly more difficult than bioconversion of

ammonia and nitrite. Provision must be made in designing mechanical

filters that are large enough to cope and easy enough to clean.

A pond that is clear and free of sediments would be a good way to

determine if the organics and solids are under control.

Controlling Algae

Algae can be controlled using various chemicals or naturally using barley

straw or barley straw extract. Caution should be used when using

chemicals to control algae as some have high copper contents. These

chemicals will also affect plants in the system and plants in your garden

when back washing filters.

Suspended algae can also be controlled to some extent with UV lights.

Numerous studies have found that barley straw can control algae when

used correctly. For the barley straw to work, aerobic conditions arenecessary. Therefore, how the barley straw is placed in the system is

important. Do not over fill the bags so that the barley straw goes

anaerobic and starts to smell.

After a time our ponds form a natural eco system. The string algae

growing on the sides of the pond tend to predominate, the suspended

single cell algae that turns water green recedes and the result is clear

water.

There are seasonal algae blooms and the water may turn cloudy in spring

but clear a month or two later. So do not over react.

Over feeding can contribute to excess nutrients ending up in the waterthat algae can utilise for growth.


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Chapter 4: CIRCULATION

Water Circulation

Importance of Internal Water Circulation

The greatest effect of water circulation is that it prevents thermal and

chemical stratification.(Boyd).

Water circulation within the pond plays a vital part in successful Koi

keeping.

In our Koi ponds water circulation is critical for moving solid and chemical

pollutants to the filters and biofilters. The water should circulate gently

around the pond as well as vertically either from top to bottom or

bottom to top. The internal circulation does not have to be at a velocitythat will over exercise and exhaust the Koi.

Circulating pond water:

Ponds will have concentrations of ammonia and low oxygenlevels in areas where the water is still.

Circulating or moving pond water establishes a uniform dissolvedoxygen profile within the water body.

The total dissolved oxygen content of the pond can be increasedwith circulation.

Ammonia is diluted throughout the pond volume. Solids can be directed to drains and removed helping to clear the

water and keep the organic load down.

To get a concept of how the water should be circulated within a pond,

look at a tropical fish or marine fish aquarium through the side and see

how the water moves and circulates.

Effects of Incorrect Circulation

An outlet directly opposite the inlet will create dead areas in the corners.

By directing the inlet water along one of the walls of the pond a circular

motion can easily be created.

dead areas

kha filtration slime city)

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