Nitrite is a substance found in aquariums that is toxic to invertebrates and fish. Many people think that nitrite completely vanishes after a tank goes through its cycle within the first 3 or 4 weeks. However, this is not true. Under normal circumstances, in aquariums, which are properly cycled, nitrite will be converted to nitrate. This substance will then go through a process called denitrification that basically converts it into nitrogen gas, which is harmless. However, before the process is completed, the nitrate converts back to nitrite. There are multiple causes that would prevent the process from reaching completion, thus leaving toxic nitrite levels in the aquarium. In order to prevent this, nitrite levels must be monitored using a nitrite test kit. However, many of them are susceptible to amine interference, which would prevent them from giving an accurate measurement, thus leaving harmful nitrite levels undetected. This is not the case with the Salifert Nitrite Test Kit, which uses special ingredients that are not affected by amine. The test uses very sharp color changes, which are easy to detect in order to provide a very fast and very accurate reading of current nitrite levels. The kit can be used for approximately 60 measurements.