Aquarium Systems SeaTest NO3 Nitrate (40 Tests) are nitrates tests for freshwater and seawater. Maximum value recommended: 50mg/l in freshwater, ideally 0.0mg/l in a reef aquarium. For approximately 40 tests. Graduated 7-colour colour scale (0; 10; 25; 50; 75; 100; >100mg/l). For a result accurate down to 0.01 mgl, use the Aquarium Systems NO3 test in combination with SeaTestControl. This device is especially and uniquely calibrated for Aquarium Systems tests. Caution, observe the precautions for use.