AMMONIA ALERT 1 YEAR MONITOR Ammonia Alert is an innovative color device for continuously detecting and monitoring toxic free ammonia. A sensor changes reversibly from yellow to green to blue, relative to the ammonia concentration. No test kits, chemicals, or procedures are needed. The device detects less than 0.05 mg/L (ppm) free ammonia and alerts you to the #1 killer before any sign of stress. It lasts over a year. This product is not recommended for use at acid pH. Marine or freshwater use. Easy to clean and wipe the dirt off without the fear to scratch the cluster screen .Seals existing scratches underneath and makes the cluster screen like new again