nitrogen & reef tanks

Reef Tank Chemistry – Nitrogen Cycle

To be successful in reef keeping, you’ll need to understand how the nitrogen cycle works, how it affects your tank’s health, and how to manage its effects.

Ammonia (NH3)

Ammonia is produced when fish waste, organic matter, and uneaten food breaks down. It is converted into nitrite by nitrogen fixing
bacteria belonging to the family Nitrobacteraceae. These include ammonia-oxidizers in geniuses of Nitrosomonas, Nitrosococcus, and Nitrospira plus nitrite-oxidizers in geniuses of Nitrococcus, Nitrobacter, and Nitrospina.  Ammonia is the leading killer organisms in reef tanks and tropical fish aquariums. New tanks going through the aquarium cycle or those heavily stocked will show ammonia readings when tested. The ideal ammonia reading is 0 ppm (parts per million).

Nitrite (NO2)

This is what Ammonia becomes when metabolized by the bacteria in your tank. It is just as toxic as ammonia to the organisms in your tank. In new tanks that have not yet cycled, nitrite levels will elevate. Nitrites eventually are converted to nitrate by the bacteria listed above growing in the tank, rock surfaces, bottom substrate, and filters. The ideal nitrite reading is 0 ppm.

Nitrate (NO3)

This is what Nitrites are converted to during the cycling process. It is not as toxic as ammonia or nitrites but still harmful and can stress your tank at high enough levels. In nature, nitrate is removed by plants and released back into the water as oxygen. In reef tanks, nitrates are removed through periodic partial water changes. nitrates should ideally remain at zero, an acceptable range for nitrate in reef tanks is 0.25 ppm – 10 ppm but up to about 20ppm may be acceptable.

Nitrogen (N)

This is what nitrates are processed into by special types of bacteria that live in oxygen poor environments (anaerobic) in your tank. It is released as nitrogen gasses into the atmosphere. Excess nitrates can also be controlled by water changes.

So you should now be asking “What is this Aquarium Cycle?”

The Aquarium Cycle or
New Tank Syndrome or
Biological Cycle or
Biological Filtration

All refer to the same thing – The Nitrogen Cycle. This cycle is what occurs naturally in the water and is what keeps the chemical balance of water at life sustaining levels for the organisms living in it. In your tank this means the establishment of beneficial bacteria in the aquarium and in the filter media that help convert ammonia to nitrite and then nitrates. To establish this bacterial growth, all you need to start is an ammonia source, oxygenated water and a surface areas they can colonize.

Successful reef keeping requires that you keep this cycle functioning properly in the contained, that is closed, environment that is your tank. You do this by testing the water for the levels of these compounds and making the required adjustments to keep them in their proper ranges such as not over feeding, water changes, and maintaining proper pH and other water parameters.

The Cycle: Ammonia -> Nitrite -> Nitrate -> Nitrogen

The cycle usually takes from 2-8 weeks to establish in a new tank. Successful reef keeping involves knowing what the cycle is, understanding how it affects your tank, and learning how to monitor the compounds created and how compensate for unwanted levels.

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