Aquarium Dilution Calculator
Calculate ideal replacement volume needed to reach an entered dissolved-concentration target.
Your result
EVERYDAYEnter your values and select calculate.
On this page How it works & practical examples
How to use the Aquarium Dilution Calculator
This is a one-step mass-balance calculation: remove part of a perfectly mixed tank, then replace the same volume. Use the same concentration unit for all three concentrations.
The calculation
Worked example
100 liters at 40 mg/L, diluted with 0 mg/L replacement water to 20 mg/L, requires a modeled 50-liter remove-and-replace step.
Assumptions and limits
No new solute is produced during the step, and replacement water must allow the lower target to be reached. A mathematically required fraction is not a species-specific safe-change recommendation or a water-treatment protocol.
Common questions
Can replacement water above the target reach a lower target?
Not through this one-step dilution model; that input is rejected.
Does this account for concentration rebound?
No. Ongoing production, filtration and biological processes are outside the model.