API Nitrite Test Kit can monitor nitrite levels from 0-5 ppm (mg/L) in freshwater and saltwater to prevent fish loss. Nitrite is produced by fish waste and uneaten fish food. Low levels of nitrite inhibit respiration and suppress the immune system; high levels may cause suffocation and fish death. With API Nitrite Test Kit, you can easily and accurately measure the nitrite level and take steps to remove it. This kit includes: 2 liquid droppers, easy to read instructions on how to test and correct water conditions, 2 color charts, and a glass test tube. 180 tests per kit. Shipping weight: 1/4 lb.