In a properly cycled aquarium, nitrite is converted to nitrate and then, if there are areas deprived of oxygen such as in live rock and other filter materials, this nitrate is converted back to nitrite and then transformed into harmless nitrogen gas. If this cycle breaks down then nitrites, which are extremely toxic to fish and invertebrates, can form in high concentration. Many nitrite test kits suffer from interference caused by amines e.g. naturally occurring and essential amino acids. This can result in a too low measured value, especially when the nitrite concentration is relatively low. Because of its unique formulation, the Salifert Test Kit does not suffer from amine interference, and offers full color development within one minute. Also, the color is very intense making the detection of even minute traces of nitrite easy. The test kit has two different scales: an ultra-low scale for nitrite-nitrogen which ranges from 0.002 - 0.12 mg/L, and a medium scale for nitrite-nitrogen which ranges from 0.02 - 1.2 mg/L. Sufficient for 50 tests. Can be used for marine water, frewshwater and garden pond water