Monitor levels of nitrate in your fresh or saltwater aquarium with API Nitrate NO3 Fresh & Salt Water Aquarium Test Kit. High levels of nitrate are caused by a buildup of fish waste, uneaten food and plant refuse causing unwanted algae growth, poor water quality and unhealthy conditions for your fish and invertebrates. This kit tests nitrate levels ranging from 0 to 160 ppm in fresh or saltwater. Just fill a test tube with water, add a few drops of both nitrate test solutions and compare your results with the color chart. If any action is needed, follow the recommendations on the chart to correct levels. Test frequently to ensure optimal water health.