Tetra Pond Water Balance 250ml keeps pond water healthy and biologically balanced. Tetra Water Balance keeps pH of the water stable and reduces the nutrient phosphate, which is key in reducing algae growth. Over time natural processes cause pond water to become unbalanced, affecting the conditions of the fish, plants and other pond life. When used regularly, Tetra Water Balance prevents the pond from becoming unbalanced, keeping it in top condition. This product also restores essential vitamins and minerals that are lost over time. Add 25ml per 1000 litres of pond water every four weeks. 250ml.