Alkaline pond water (pH 7-14) is usually caused by using cement around the pond that drops into the water or calcium rich rock around the edge of your pond that allows rain to run over it and into the pond. Once your pond gets above pH 8, it needs reducing to keep the pond water safe. This easy to use product adjusts the pH to keep it safely in the 'Safe range' for a pond which is between 6.5 - 8. (pH must be stable within this range). Treats 5,675 Litres.