pH is the measure of acidity or alkalinity of water. Incorrect pH causes fish stress, which is one of the main causes of ill health,
poor colouration and a failure to breed.
Many factors influence the pH of a pond water, including tap water!
Causes of high pH include: water contact with concrete, cement, paving slabs and green water.
Causes of low pH include: soft tap / rainwater, stocking density, fish waste, over feeding and decaying vegetation.