sera pH-minus effectively lowers the pH value in freshwater aquariums . If the pH value is greater than 7.0 and the KH value is greater than 6 °dKH, add 5 ml of sera pH-minus per 20 liters of aquarium water. For pH values of 7.0 or less, add 1 – 2 ml of sera pH-minus per 20 liters of water.