|Danger:||> 10 ppm|
Anyone with a freshwater background will know that nitrite is toxic to fish. This belief in the toxicity of nitrite has carried over in to the marine hobby, when in fact nitrite is not very toxic at all. Other than using nitrite readings to evaluate the biological filtration in a new tank, it can pretty much be ignored.
What is nitrite?
Nitrite is the first product of the nitrification of ammonia. Bacteria utilise ammonia for energy and the product is nitrite. It is often present during the establishment period of a new tank but after that it is rarely detectable as it is quickly utilised by bacteria which oxidise it to nitrate. Additionally, algae and even some animals can use nitrite as a source of nitrogen.