An old water aquarium is an aquarium that does not require regular water changes. Only the evaporated water is replaced or, if necessary, a partial water change is carried out. It is therefore a water-saving form of aquaristics . It is trusted by the followers of the Altwasseraquaristik that the self-cleansing of sewage sludge ( sludge ) in the filter and the substrate and the plants are sufficient for keeping the water. For a functioning backwater aquarium, an adapted stocking density with fish and the type and amount of feeding also play a role.
A water change that may be necessary is determined by checking the water values by means of analyzes or by observing animals and plants. A water change may be necessary, especially after the outbreak of diseases due to the introduction of new plants or animals.
- Gerd Kassebeer: Old water? Olaf Deters' private website, February 2003.