Test intended for measuring the concentration of nitrate (NO3-) within the range of 0-100 mg/l in fresh and salt water. It is convenient and extremely easy to use. The relevant reagent solution is added to the water drop by drop until the colour of the sample changes, then it should be compared with the colour scale provided. The sources of nitrates are fish excreta, uneaten food and other organic wastes which accumulate in the aquarium and are broken down by the bacteria. Sometimes nitrate concentration increases reaching dangerous levels and causing massive algae proliferation. Systematic monitoring of nitrate concentration prevents conditions dangerous to fish. For further water inspection we recommend other Tropical tests.