Estimate an aquarium nitrate maintenance interval, dilution, or water change volume using actual water volume and measured nitrate values. The nitrate model is not a complete water-quality or fish-health assessment.

Nitrate-only, perfectly mixed model. Use the same nitrate reporting basis for every reading and rate (NOโ‚ƒ or NOโ‚ƒ-N). Choose a target for your species; condition replacement water and match temperature and chemistry. Large or repeated changes need care.

Test the replacement water; enter 0 only if measured or established.

Use repeated measurements under similar feeding and stocking. Presets are illustrative.

Container estimate

Related Calculators

Water Change Formula

The formula below gives the percentage of actual tank water replaced in one drain-and-refill. Select Water change percentage in the calculator to use it.

WC = WCV / WT ร— 100

Variables:

  • WC is the Water Change (%)
  • WCV is the volume of the water change (L) 
  • WT is the volume of the tank (L) 

To calculate the water change percentage, divide the volume of the water change by the volume of the tank, then multiply by 100.

For nitrate dilution, the fully mixed concentration after a change is Cafter = (1 โˆ’ f) ร— Ccurrent + f ร— Csource, where f is the fraction replaced. With constant daily rise r, the nitrate-only maintenance interval has an upper bound of f ร— (Ctarget โˆ’ Csource) / r days. Replacement water must be below the target when r is positive. Use a measured rise rate and a species-appropriate target; illustrative rate presets are not stocking recommendations. The first deadline depends on the current concentration after any modeled corrections, and can differ from the repeating interval. Do not round the upper bound upward.

How to Calculate Water Change?

The following steps outline how to calculate the Water Change.

  1. First, determine the volume of the water change (L). 
  2. Next, determine the volume of the tank (L). 
  3. Next, gather the formula from above = WC = WCV / WT * 100.
  4. Finally, calculate the Water Change.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

volume of the water change (L) = 4

volume of the tank (L) = 10

WC = WCV / WT * 100 = 4 / 10 * 100 = 40%.