Nitrate is one of the final products of biological removal of ammonia. While it is not toxic, levels above 10 PPM will inhibit coral growth and may irritate invertebrates. High levels will indicate not enough water changes, too high a fish load or in marine applications, not enough area for denitrifying bacteria to live. This test kit includes a test vial, two reagents and a color chart to determine the amount of total nitrate in the aquarium. There are two scales on the chart measuring 0.2 to 10 PPM and 2 to 100 PPM (Mg/L). This test kit will do 50 tests.