The best possible pH value for keeping most freshwater fish and plantes is the neutral range around 7. JBL pH-Minus lowers excessively high pH values in your aquarium and promotes fish health via added natural oak extract. JBL pH-Minus is phosphate free. Any variation in the pH level should be checked with a pH test. The CH (carbonate hardness) should be checked before use and adjusted to 4-8dCH (e.g. with JBL AquaDur plus).Dosage: pH value above 8: 10 ml for 40 litres of aquarium water, pH value between 7 and 8: 10 ml for 80 litres of aquarium water.