Check your aquarium's ammonia levels quickly and easily with API's Ammonia NH3/NH4 Aquarium Test Strips. Ammonia is toxic to fish and can cause gill damage, stress and even lead to fish loss. Regular testing is recommended because ammonia levels can build quickly due to fish waste and uneaten food. Simply dip the test strip into the water, then compare the results with the precise, easy-to-read color-coded chart to determine if any action should be taken. The chart includes recommendations on how to treat the water and neutralize ammonia. These test strips are suitable for both fresh and saltwater.