Stressed fish causes diseases. One of the main causes of pond fish stress is an unsuitable pH. pH is a measure of the acidity or alkalinity of the pond water. The ideal pH is between 7.0 (neutral) and pH8.0 (slightly alkaline) but pH 6.5-8.5 is acceptable. pH Adjuster for Ponds will increase or decrease pH levels to within the safe level to help maintain a healthy pond environment for fish, plants and other pond life. Alkaline PH Adjuster is used to decreasing pH levels in ponds which have a tested pH of above 8.5 whilst pH adjuster for acid ponds is used to increasing pH levels in ponds which have a tested pH of below 6.5. To be used in conjunction with a pH test kit.