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Aquarium Calculators

Aquarium Water Change Calculator

Water to change, dechlorinator dose and the nitrate reduction achieved.

Enter values

Results update as you type.

Result

Water to change

45 litres

Match the new water’s temperature to the tank within a degree or two, and always dechlorinate before it goes in.

In US gallons
11.89
Nitrate after the change
30 ppm
Nitrate removed
10 ppm
Dechlorinator needed
4.5 ml
Water used per month
180 litres
Buckets (10 L)
5

About the Aquarium Water Change Calculator

Water to change, dechlorinator dose and the nitrate reduction achieved.

Also known as: water change percentage, aquarium maintenance calculator, dechlorinator dose, partial water change.

How to use this calculator

  1. Enter tank water volume, change percentage, current nitrate, dechlorinator dose and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

change volume = tank volume × change percentage

Worked example

Using the values pre-filled in the calculator above:

  • Tank water volume = 180 litres
  • Change percentage = 25 %
  • Current nitrate = 40 ppm
  • Dechlorinator dose = 5 ml per 50 L
  • Changes per month = 4

the calculator returns:

  • Water to change: 45 litres
  • In US gallons: 11.89
  • Nitrate after the change: 30 ppm
  • Nitrate removed: 10 ppm