Why this number
A 30% water change means 30% of usable water, not 30% of the glass box. This tool converts percent → liters/gallons so buckets and python hoses are not guesswork.
How to use
- Enter tank size and substrate depth.
- Choose percent (common: 20–50%).
- Match dechlorinator dose to the volume you actually add back.
FAQ
How often should I change water?
Depends on stock and feeding. Many planted tanks do weekly partials; test nitrate if unsure.
Bigger changes safer?
Not always — match temperature and parameters; huge swings stress livestock.