Pond Health Check tests three water parameters (pH Ammonia Nitrite) with full instructions to help diagnose and treat sickness in pond fish optimum levels and suggestions for correction. pH is the measure of acidity or alkalinity of the water in a pond. Pond fish prefer the water to be between 7 & 8 fluctuations outside these values can cause stress to the fish. Ammonia is excreted by the fish as a waste product too much ammonia will cause major health problems so needs testing regularly. Nitrite is produced by the beneficial bacteria in the pond and filters as they break down the harmful waste ammonia excreted by the fish. Nitrite can affect the health of fish but is not as toxic as ammonia so test regularly.