Aquarium Water Change Calculator

Enter tank volume and change percentage.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

A partial water change removes a set percentage of an aquarium’s water — commonly 10–25% weekly — to dilute accumulated nitrates and other dissolved waste that a filter’s beneficial bacteria don’t remove, without disturbing the whole tank’s biological balance the way a full change would. The volume to remove is simply tank volume × change percentage.

Fishkeepers and aquarists follow this routine as a core part of tank maintenance, since nitrate buildup between water changes is one of the leading causes of fish stress and disease in both freshwater and reef tanks. This calculator takes your tank volume and desired change percentage and reports how much water to remove, in both gallons and liters, along with what remains in the tank.

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