Aquarium water change tracker for cleaner, safer tanks
Water changes are simple, but forgetting them is where the wheels come off.
Use TanksConnected to log water changes and connect them with test results, stocking and ongoing tank health.
This public preview gives you a quick feel for the feature. Create a free account to save your own tanks, add livestock, record test results, and keep your aquarium history together inside TanksConnected.
Water change and nitrate dilution calculator
Estimate how much water to change, what that may do to nitrate, and roughly how much dechlorinator the replacement water needs.
Need the maintenance side too? Read the aquarium water change guide for frequency, safe technique and routine-care guidance.
Water change details
Use actual tank volume where possible, not just advertised tank size.
Divide the product's stated ml dose by the volume it treats, using the volume unit shown above.
Estimated result
This is simple dilution maths. It does not replace testing.
Common water change and nitrate questions
Use the calculator for quick water change estimates and nitrate dilution checks.
- How much water should I change in my fish tank?
- Water change calculator for aquariums
- Nitrate dilution calculator
- How much will a 50% water change lower nitrate?
- How do I lower nitrate in a fish tank?
- How many litres is a 30% water change?
Extra water change guidance, FAQs and related tools
Routine changes
Weekly or regular water changes keep nitrate and dissolved waste under control.
Heavy-stocked tanks
Large or messy fish often need bigger changes, stronger filtration and closer nitrate monitoring.
Trend spotting
A log helps show whether your current schedule is enough or needs adjusting.
Water changes are still king
Filters process waste, but water changes remove what builds up. Tracking them keeps the basic husbandry honest.
Frequently asked questions
Why should I track aquarium water changes?
Tracking aquarium water changes helps you see whether your maintenance routine is consistent and whether nitrate, water clarity or fish behaviour improves after changes.
How often should aquarium water changes be done?
Water change frequency depends on tank size, stocking, feeding, filtration and nitrate build-up. Many aquariums benefit from weekly changes, but heavily stocked tanks may need larger or more frequent changes.
Should I record the percentage of water changed?
Yes. Recording the approximate percentage changed gives better context than only recording the date, especially when comparing water changes with nitrate readings or fish health.
Can filters replace water changes?
No. Filters process waste, but they do not remove everything that builds up in aquarium water. Water changes remain one of the most reliable parts of long-term fish tank care.
Is this an aquarium water change calculator?
Yes. The free aquarium water change calculator works out how much replacement water a percentage change represents for your tank. Enter the aquarium volume and planned water change percentage to see the amount of water to remove and replace.
How many litres or gallons is my water change?
Enter your aquarium volume and chosen water change percentage and TanksConnected will calculate the replacement amount in your selected measurement system. For example, a 30% water change replaces 30% of the tank volume rather than a fixed number of litres or gallons.
Can the calculator estimate nitrate after a water change?
Yes. The nitrate dilution calculator can estimate the nitrate level after a water change using the current aquarium nitrate, the nitrate in the replacement water and the percentage changed. It is simple dilution maths and should still be checked with a water test.