Calculator
Water Change Calculator
Calculate exactly how much water to change to lower nitrates, phosphates, or other parameters to your target level.
Tank Size
Parameter to Lower
Keep below 20-40 ppm
How It Works
Water changes dilute dissolved substances. The formula is:
New Level = Current Level × (1 - Change%)
This assumes your replacement water has 0 of the parameter you're trying to lower. If your tap water has nitrates, for example, you may need larger changes to reach your target.
Quick Reference
25%
Reduces by 25%
Weekly maintenance
50%
Reduces by 50%
Monthly deep clean
30% × 2
Reduces by 51%
Safer than 50% single
25% × 3
Reduces by 58%
Gradual reduction
Track Your Water Changes
Log your water parameters over time, get automatic change reminders, and see trends with beautiful charts.
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