Nitrogen compounds

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Ammonia, nitrite, and nitrate are the major nutrient ions produced in a marine aquarium. They are components of the biological filtration process, which is essential to the survival of the aquarium inhabitants.

Protiens, which are found in every kind of food, are amino acid compounds. These amino acid compounds eventually wind up either in the protiens of the animal that has consumed the food or in the water as excreted ammonia. Fish and inverebrates do not tolerate large amounts of ammonia in the water.

Nitrifying bacteria cultivated in the aquarium convert the ammonia into nitrite and then into nitrate. Tests for ammonia and nitrite are used to determine if these bacteria processes are proceeding correctly. Test for ammonia and nitrite should always be zero after a population of nitrifying bacteria is established in the aquarium.

Nitrate is the end product of bilogical filtration and is tolerated to some degree by marine organisms. Tests for nitrate should be performed on a weekly basis. water changes should be carried out with sufficient frequency and in amounts large enough to keep the nitrate concentrations rather low, max. 20 mg/l or less. ideally less than 5 mg/l (nitrate-nitrogen).

Nitrate is not toxic to marine organisms in small amounts. The accumulation or sometimes depletion of other compounds as the result of insufficient water changes may be harmful to the aquarium's inhabitants. Such effects are often incorrectly attributed to nitrate, allthough, nitrate accumulation can be a convenient indicator of the need to perform a partial water change.