Aquarium Water Change Calculator
Calculate water-change volume and dilution of an entered nitrate level.
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What this tool does
Calculate water-change volume and dilution of an entered nitrate level. Assumes complete mixing with no additional nitrate production during the change.
How to use the Aquarium Water Change Calculator
- Enter or select system water volume in gal.
- Enter or select water change (%).
- Enter or select current nitrate (ppm).
- Enter or select replacement nitrate (ppm).
- Read the calculated result; change any measurement to compare alternatives.
Formula
change gallons=volume×percent/100; final concentration=current×(1−percent/100)+replacement×percent/100
- volume
- System water volume (gal, before metric conversion)
- percent
- Water change (%)
- current
- Current nitrate (ppm)
- new
- Replacement nitrate (ppm)
Assumes complete mixing with no additional nitrate production during the change.
Worked example
For aquarium water change calculator, the following measurements illustrate the exact method: System water volume: 75; Water change (%): 20; Current nitrate (ppm): 40; Replacement nitrate (ppm): 0.
Inputs
- System water volume75 gal
- Water change (%)20
- Current nitrate (ppm)40
- Replacement nitrate (ppm)0
Result
- Water to change15 gal
- Estimated nitrate after change (ppm)32
Results explained
- Water to change
- Water to change from the formula above, expressed in gal before metric conversion. Assumes complete mixing with no additional nitrate production during the change.
- Estimated nitrate after change (ppm)
- Estimated nitrate after change (ppm) from the formula above. Assumes complete mixing with no additional nitrate production during the change.
Frequently asked questions
change gallons=volume×percent/100; final concentration=current×(1−percent/100)+replacement×percent/100
No. Individual animals differ. Consult your veterinarian before changing feeding or treatment, and seek immediate veterinary care for poisoning concerns.
Assumes complete mixing with no additional nitrate production during the change.
Use current measured weight, actual food or product label values, and the dates or water readings requested. Check units before entering any value.
Verify if the animal is ill, pregnant, growing unusually, or on a special diet. Aquarium chemistry changes should be measured gradually and checked against product instructions.