Nitrite (NO2-) results in aquarium water as the natural by-product of decomposition of ammonia due to beneficial biological filtration activity. Nitrite is toxic to fish life, and is further decomposed to nitrate, but interruptions or inefficiencies in filtration can lead to its accumulation. Nitrite concentrations as low as 1.6 mg per liter of water can adversely affect your fish, and in severe cases is fatal. Regular testing for nitrite will ensure optimum water quality and verify filter performance. The Tetratest Nitrite (NO2-) kit includes two 10-ml test reagents (#1 & #2), test vial, color scale, instructions and recommendations and 45 tests.
Note:
For Freshwater (including outdoor ponds), Brackish and Saltwater."