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Calculate aquarium volume and water changes
How much water is actually in your tank? Internal dimensions and the water depth give you a first estimate. If you measured the water when filling it, you can use that amount directly.
The dimension formula applies to rectangular tanks. Internal measurements and the actual water line are more useful than the outside dimensions on the box. Displacement is an estimate; measuring the litres added during filling gives a better starting point.
What does the water change amount mean?
The chosen percentage is an input for the calculation. How much water to change, and how often, depends on the animals, feeding, filtration and measured water conditions. The water care guide explains these factors.
This calculator does not assess water quality or recommend stocking levels. Tanks with the same volume can have different footprints and swimming space, while individual species have different needs.