AMMONIA ALERT-.No tests, no strips. Continuously monitors free ammonia. Marine and freshwater. Ammonia Alert is an innovative color-changing sensor for detecting and monitoring toxic free ammonia. A sensor reversibly changes from yellow to green to blue, depending on the ammonia concentration. No test kit, chemical or procedure is required. The device detects less than 0.05 mg/L (ppm) of free ammonia and alerts you before any signs of stress. One year shelf life. This product is not recommended for use in acidic pH. Use in marine or freshwater.