Introduction to Nitrite

Aerobic bacteria of the genus Nitrosommonas in the biological filter, oxidize toxic Ammonia to Nitrite. This substance is only slightly less toxic than Ammonia (NH₃), but in the biological filter of a well established aquarium Nitrite (NO₂-) is quickly transformed into the relatively harmless Nitrate (NO₃-), by yet another aerobic bacteria, called Nitrobacter.

New Aquariums

In a newly set up aquarium a high Nitrite level is a normal phenomenon. It means that the Nitrosomonas bacteria have started the nitrification process and produce Nitrite out of Ammonia. Nitrobacter is however not yet present in sufficient quantities to transform Nitrite into Nitrate.

In a newly set up aquarium we advise that you test for Nitrite daily for at least two weeks.

Only this, together with testing for Ammonia (use Red Sea’s Ammonia Mini-Lab), will tell you when it is safe to put (more) fish into your aquarium. After this two week period, especially in the marine aquarium, one should start testing for Nitrate, using Red Sea’s Nitrate Mini-Lab.

Established Aquariums

Nitrite should be tested when there is suspicion of a malfunctioning biological filter. After a long period of time, the filter can get dirty causing Oxygen shortage leading to high Nitrite levels.Since in this case toxic Ammonia can also be present in the aquarium, it is advisable to test for Ammonia, using Red Sea’s Ammonia Mini-Lab.

Recommendations

A concentration as low as 0.1 ppm is already harmful to many marine invertebrates. Concentrations above 0.3 ppm are harmful for marine and freshwater fish. A typical behavioral symptom of acute Nitrite poisoning is listlessness of the fish.

Lower Nitrite levels stress and weaken the fish, making them susceptible to parasitic infections such as white spot.

The immediate short term measure should be to change 20 % of the aquarium water every day. For the marine aquarium we advise changing the water using Red Sea’s Red Sea Salt, until the NO₂ levels drops below 0.2 ppm. Red Sea Salt is especially useful in emergency situations like this, since it can safely be used immediately after dissolving, the pH and alkalinity being at the natural level. At the same time we recommend to remove fish if possible, reduce feeding, clean the filter and inoculate it with some fresh material out of a good working biological filter, or use a freeze dried bacteria preparation.