API Ammonia Test Kit tests Ammonia which is the number one killer of tropical fish. Fish continually release ammonia into the aquarium through their gills, urine and solid waste. Uneaten food and decaying organic matter also add ammonia to the water. Even small amounts of ammonia stress fish, large amounts of ammonia will kill fish. So regular testing for ammonia is important to maintain healthy aquatic life. Kit contains 2 bottles of liquid reagent, 2 laminated, computer calibrated colour cards, glass test tube with snap-tight cap, step by step instructions and information on how to correct unsafe conditions.