The Salifert Nitrite Test Kit measures the extremely dangerous levels of nitrite that build up in aquariums due to interference with the nitrogen cycle. Nitrites are usually converted to nitrates and removed throughout the nitrogen cycle, but when the cycle cannot be completed, these nitrites begin to accumulate and harm your tank inhabitants. Unlike other nitrate testers, the Salifert Nitrite Test Kit is not affected by the presence of amines. Even the smallest traces of nitrite will be detected with a noticeable color change in the test kit..