What Importance Is Nitrite & Nitrogen to a Fish Tank?

To maintain a balanced nitrogen aquarium cycle for your fish, it is important that nitrite levels are maintained at a low level, as nitrites are toxic and in large amounts can kill fish. The "nitrogen cycle" is the biological process that converts ammonia into nitrites and then into nitrates. The aquarium nitrogen cycle begins when fish waste or uneaten fish food decomposes and converts from ammonia to nitrites in aquarium water.

  1. Aquarium Nitrogen Cycle

    • The aquarium nitrogen cycle can be broken down into three distinct stages that will last approximately four to six weeks in total before you have to cycle the aquarium tank water. In the first stage, which lasts two to three weeks, as the fish produce fish waste or perhaps dead fish appear in the water, ammonia is created. It is important to clean the tank regularly to prevent toxic ammonia build up. At phase two, necessary bacteria is building up, which will convert the ammonia into nitrite over roughly two weeks. In the third stage, there will be a large bacteria colony in the aquarium to convert nitrite into less harmful nitrate, according to the website Tropical Fish Success.

    Beginning Nitrogen Cycle

    • To begin the cycling process for your aquarium so that you will end up with the necessary mount of bacteria needed to complete the process of breaking down the fish waste and maintain healthy fish, add a few fish at a time. Begin lightly feeding so that there is no an accumulation of uneaten food which will potentially create additional ammonia buildup. Try to secure "aquarium plants, gravel or filter media from a mature tank which will introduce some of the necessary bacteria and possibly reduce cycling time," states the website The Tropical Tank -- The Basics of Cycling.

    High Nitrite Levels

    • Aquarium fish will not remain healthy in a mature tank if the nitrite levels remain high after the second stage or two-week period where the nitrites are being converted into nitrates. A safe level for nitrite levels in an aquarium tank water should be less than 0.1 parts per million (ppm). If it is at this level or higher, it means that the nitrite is not being properly oxidized by the bacteria which convert it into nitrate. If the fish appear to be gasping and there is a rapid movement of the gills, the fish could be suffocating, because nitrite binds to the haemoglobin in the blood.

    Minimizing Fish Deaths in Tanks

    • There are several precautions that can be undertaken to minimize the possibility of fish deaths resulting from increased ammonia in the aquarium tank during the cycling process. If the water has been changed regularly and high ammonia levels persist, then consider commercial products like Amquel. Amquel will neutralize the ammonia's toxicity, yet still allow for the nitrification process to continue. Be aware that if Amquel is used, any ammonia testing kits could register false readings concerning levels of Ammonia present, according to the Duke University Department of Computer Science. In addition, increase biological filtration and vacuum aquarium gravel in sections during every water change.