How many liters do you need to change? Straight from a percentage or from your current and target nitrate – no registration needed.
Routine changes: 20–30% per week is a solid default for most community tanks.
Nitrate target: The required change fraction is 1 − (target ÷ current). The closer target and current are, the smaller the change can be.
Split large changes: Doing over 50% at once can stress sensitive animals with sudden parameter swings – better to spread it across two smaller changes over a few days.
Nitrate rises again afterward: The calculation applies to the moment right after the change – fish and filter bacteria keep producing nitrate continuously.
Instead of recalculating every time: your tank volume is saved, every water change is logged, and you see the nitrate trend over time instead of just a snapshot.
Log every change. Always see the last change date and upcoming reminders.
Log NO₂ and NO₃ after every change – and watch the trend over weeks.
Never forget a water change again – automatic reminders on your own schedule.
Work out net liters from your tank dimensions – the basis for this calculator.
Mixing ratio of RO/DI and tap water for your next water change.
How many fish can your tank handle? Check stocking density based on net volume.
Liters, gallons, °C/°F, GH/KH to ppm – every aquarium unit in one place.
Create your tank, track water changes and test results – free, no download.
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