Seachem Ammonia Alert Sensor

Ammonia Alert detects and continuously monitors free ammonia in marine or freshwater aquariums. Simply place it in the aquarium (using the provided suction cup) and get a quick reading anytime. It will correctly read ammonia levels even when ammonia removers are in use. The unit consists of a waterproof reference color card and a sensor. The sensor, located in the center of the reference scale, changes reversibly from yellow to green to blue relative to the ammonia concentration. Properly maintained, the sensor has a useful life of over a year.