Acid pond water can be caused by a high level of organic waste. This pH adjuster is for increasing pH levels in ponds which have a tested pH of below 6.5. It adjusts the pH of pond water for optimum fish health, keeping your fish stress-free. The ideal pH is between 7.0 (neutral) and pH 8.0 (slightly alkaline), but pH 6.5-8.5 is acceptable. One level measure of Blagdon pH Adjusters treats 285 litres (63 gallons) of water. Help maintain a healthy pond environment, it is totally safe for all pond fish, plants, and other pond life.