Water Change Calculator
Calculate the exact water change percentage needed to reach your target TDS without stressing your shrimp.
How to Use This Calculator
Step-by-Step Guide
- 1
Enter your tank volume (the actual water volume, not tank size)
- 2
Measure and enter your current tank TDS
- 3
Enter your target TDS (where you want to end up)
- 4
Enter the TDS of your replacement water (0 for RO, or your remineralized water TDS)
- 5
The calculator will show you the exact percentage and volume to change
Water Change Guidelines
Safe Zone: Under 25%
Water changes under 25% are generally safe for shrimp. This is the recommended approach for regular maintenance.
Caution: 25-50%
Larger changes should be done slowly using a drip method. Consider splitting into two changes on consecutive days.
High Risk: Over 50%
Very large water changes can cause osmotic shock. Always split into multiple smaller changes over several days.
Understanding the Formula
This calculator uses dilution math to determine how much water you need to change:
Change % = (Current TDS - Target TDS) / (Current TDS - New Water TDS) x 100
Volume to Remove = Tank Volume x (Change % / 100)
The formula works in both directions. If your tank TDS is too high (common with evaporation), you'd use lower-TDS water like RO. If it's too low, you'd use water with higher TDS than your tank.
Why TDS-Based Water Changes?
TDS (Total Dissolved Solids) gives you a quick snapshot of your overall mineral content. While it doesn't tell you exactly what's dissolved (you need GH/KH tests for that), it's excellent for maintaining consistency and catching parameter drift before it becomes a problem. Learn more in our TDS guide.
Track Water Changes in the App
Log your water changes, track TDS over time, and get reminders for your maintenance schedule. See how your parameters change with beautiful graphs.
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