Start by measuring the KH level of water. This should be at least 4°dH to prevent a pH decrease. Add 5 ml per 100 litres of water every two days until a level of 4°dH is reached.
Dosage without fish and plants: The KH level should be 2°dH. To reduce the KH level by 1°dH, add 10 ml per 100 litres of water. To reduce the level by 2°dH, add 20 ml per 100 litres of water, and so on.