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Understanding the Nitrogen Understanding the Nitrogen Cycle in your AquariumCycle in your Aquarium

A presentation forA presentation for

The Angelfish Society The Angelfish Society February 21, 2010February 21, 2010

By Tamar StephensBy Tamar Stephens

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Do you know…?Do you know…?

Why is the nitrogen cycle important?Why is the nitrogen cycle important? How does nitrogen get into an aquarium?How does nitrogen get into an aquarium? How does ammonia form in an aquarium?How does ammonia form in an aquarium? How does a cycled aquarium get rid of How does a cycled aquarium get rid of

ammonia? Where does it go?ammonia? Where does it go? What is the difference between ammonia What is the difference between ammonia

and ammonium?and ammonium? How does pH affect the formation of How does pH affect the formation of

ammonia?ammonia?

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Why is Nitrogen Important?Why is Nitrogen Important? Nitrogen is a key constituent of living tissue. Nitrogen is a key constituent of living tissue.

Nitrogen is used in the formation of amino acids, which Nitrogen is used in the formation of amino acids, which are the building blocks of proteins. are the building blocks of proteins.

Proteins are used to build tissues and other important Proteins are used to build tissues and other important substances in our bodies including muscle tissue, organ substances in our bodies including muscle tissue, organ tissue, enzymes. tissue, enzymes.

The general structure of an “alpha” amino acid.

(Figure from Wikipedia.)

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Where does nitrogen come from?Where does nitrogen come from?

The atmosphere is a huge reservoir for nitrogen, The atmosphere is a huge reservoir for nitrogen, consisting of about 80% nitrogen gas.consisting of about 80% nitrogen gas.

Nitrogen gas consists of two atoms held together with a Nitrogen gas consists of two atoms held together with a triple bond. This bond is very hard to break, so most triple bond. This bond is very hard to break, so most nitrogen in living organisms is recycled in more available nitrogen in living organisms is recycled in more available forms.forms.

NΞN

The triple bond in nitrogen gas is very difficult to break.

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Nitrogen Cycle: Nitrogen Cycle: Simplified Global ViewSimplified Global View

In a simplified view, the In a simplified view, the nitrogen cycle has these nitrogen cycle has these steps.steps.

Nitrogen gas from the Nitrogen gas from the atmosphere is converted atmosphere is converted into a usable form by into a usable form by nitrogen fixing bacteria.nitrogen fixing bacteria.

The nitrogen compounds The nitrogen compounds are taken up by plant are taken up by plant tissue.tissue.

Plant tissue is eaten by Plant tissue is eaten by animals.animals.

Decaying plant and Decaying plant and animal wastes are cycled animal wastes are cycled back to the soil to be back to the soil to be taken up by plants again. taken up by plants again.

Figure from:

www.kidsgeo.com/images/nitrogen-cycle.gif

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How does nitrogen get into the How does nitrogen get into the aquarium?aquarium?

Nitrogen enters the aquarium from:Nitrogen enters the aquarium from: Bodies of the fish Bodies of the fish Fish foodFish food Plants placed in the aquarium. Plants placed in the aquarium.

Every time you add fish, add a plant, or Every time you add fish, add a plant, or feed your fish, you are adding nitrogen to feed your fish, you are adding nitrogen to the aquarium. the aquarium.

LetLet’’s find out what happens to it in the s find out what happens to it in the aquarium.aquarium.

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Nitrogen Cycle in the AquariumNitrogen Cycle in the Aquarium 3 steps of the 3 steps of the

nitrogen cycle nitrogen cycle occur in the occur in the aquarium.aquarium.1. Organic wastes 1. Organic wastes

(fish feces, dead (fish feces, dead fish, decomposing fish, decomposing plant matter, etc.) plant matter, etc.) decompose, decompose, producing producing ammonium.ammonium.

2. Ammonium is 2. Ammonium is converted to nitrite converted to nitrite by bacteriaby bacteria

3. Nitrite is converted 3. Nitrite is converted to nitrate by to nitrate by another type of another type of bacteriabacteria

1 - Organic wastes decompose into ammonium

2 - Ammonium is converted to nitrite by “nitrobacter” bacteria.

Organic matter enters aquarium (fish, fish food, plants)

3 - Nitrite is converted to nitrate by “nitrosomonas” bacteria.

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Is there really a Is there really a ““cyclecycle”” in the in the aquarium?aquarium?

Go back to the previous slide. Is this really a cycle?Go back to the previous slide. Is this really a cycle?

Where does the nitrate go? Does it get recycled in the Where does the nitrate go? Does it get recycled in the aquarium? aquarium?

Cycle or not?Cycle or not?

No – the nitrate does not get recycled. It No – the nitrate does not get recycled. It builds up in the water. To a limited extent, builds up in the water. To a limited extent, it can be taken up by aquarium plants, but it can be taken up by aquarium plants, but not sufficiently for you to rely on. not sufficiently for you to rely on.

To complete the cycle, we need to remove To complete the cycle, we need to remove the nitrate and put it back into the global the nitrate and put it back into the global nitrogen cycle. We do this through water nitrogen cycle. We do this through water changes.changes.

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Nitrogen Cycle in the AquariumNitrogen Cycle in the Aquarium

1 - Organic wastes decompose into ammonium.

2 - Ammonium is converted to nitrite.

Organic matter enters aquarium (fish, fish food, plants). 3 - Nitrite is

converted to nitrate.

Nitrates are removed through water changes.

Here we can see the 3 steps of the nitrogen cycle that occur in the aquarium.

Nitrogen in your TankNitrogen in your TankNitrobacter not NitrospiraNitrobacter not Nitrospira

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What do we mean by a What do we mean by a ““cycledcycled”” aquarium?aquarium?

A A ““cycledcycled”” aquarium is one that has an established population of the aquarium is one that has an established population of the bacteria that convert ammonium to nitrite and nitrite to nitrate.bacteria that convert ammonium to nitrite and nitrite to nitrate.

The bacteria that decompose wastes, producing ammonium, grow The bacteria that decompose wastes, producing ammonium, grow

very quickly. very quickly. It takes longer for the other types of bacteria to develop to convert It takes longer for the other types of bacteria to develop to convert

ammonium to nitrite, and nitrite to nitrate.ammonium to nitrite, and nitrite to nitrate.

In a cycled aquarium, these steps occur very quickly so there is no In a cycled aquarium, these steps occur very quickly so there is no build up of ammonium.build up of ammonium.

LetLet’’s take a closer look at each step.s take a closer look at each step.

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Step 1 - AmmoniumStep 1 - Ammonium Ammonium is an ion that is fairly non-toxic to fish. Ammonium is an ion that is fairly non-toxic to fish.

However it easily changes to a highly toxic form, However it easily changes to a highly toxic form, ammonia, which can stress and kill fish quickly.ammonia, which can stress and kill fish quickly.

If the pH is acidic (<7) the ammonium ion is favored. If the pH is acidic (<7) the ammonium ion is favored. When the pH is basic (>7), the ammonium ion is quickly When the pH is basic (>7), the ammonium ion is quickly turned to ammonia, which is deadly for the fish. turned to ammonia, which is deadly for the fish.

Your aquarium should have a pH of 8.3. High Ammonia can change this pH.

Buffers can absorb excess Hydrogen ion to control the pH. Buffers also contain Phosphates which can damage your fish and cause algae growth. Use in moderation.

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Steps 2 and 3 - Nitrite and NitrateSteps 2 and 3 - Nitrite and Nitrate

Nitrite, like ammonia, is also very toxic to fish. Nitrite, like ammonia, is also very toxic to fish. NO2NO2

Nitrate is less toxic in low to moderate NO3 Nitrate is less toxic in low to moderate NO3 concentrations, but becomes stressful as concentrations, but becomes stressful as concentrations build up.concentrations build up.

The bacteria that do these steps of the cycle are The bacteria that do these steps of the cycle are aerobic. That means they need oxygen. If you aerobic. That means they need oxygen. If you dondon’’t have a good supply of oxygen in the t have a good supply of oxygen in the aquarium, or if you get a sudden increase in the aquarium, or if you get a sudden increase in the organic wastes, the bacteria can deplete the water organic wastes, the bacteria can deplete the water of oxygen quickly, which will also kill fish. of oxygen quickly, which will also kill fish.

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Possible Tank Scenarios Possible Tank Scenarios What could cause Ammonia to be too high?

What could cause Nitrite to be too high?

What could cause Nitrate to be too high?

What could cause Nitrate to be too low?

What could cause pH to be too low?