Water Change Calculator
Calculate how water changes reduce concentrations in your aquarium.
Water Change Calculator
Calculate how water changes reduce concentrations
Formula
C_new = C_old × (1 - change%)How to Use
- 1Enter tank volume — Input your aquarium water volume in gallons or liters.
- 2Set current levels — Enter the current nitrate or pollutant concentration (ppm).
- 3Choose change percentage — Select how much water you plan to change (e.g., 25%, 50%).
- 4See the results — View the new concentration after the water change and plan your schedule.
Frequently Asked Questions
How often should I change aquarium water?
Most tanks benefit from 25-30% weekly water changes. Heavily stocked tanks may need more frequent changes.
Is a 50% water change safe?
Yes, as long as the replacement water matches temperature and pH. Large changes are sometimes needed for high nitrate levels.
What nitrate level is too high?
Keep nitrates below 40 ppm for most freshwater fish, and below 20 ppm for sensitive species or planted tanks.
Does dechlorinator affect water changes?
Always use dechlorinator when adding tap water. It neutralizes chlorine and chloramine that are harmful to fish.