How to Do an Aquarium Water Change
The single most important maintenance habit.
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How much, how often
A 20–30% water change weekly suits most tanks. Heavily stocked tanks need more; lightly stocked planted tanks can sometimes do less. Consistency beats big occasional changes.
Match temperature and dechlorinate
Refill with water close to tank temperature and always add a dechlorinator — tap water's chlorine and chloramine kill beneficial bacteria and harm fish gills.
Siphon the substrate
Use a gravel vacuum to pull out detritus from the substrate as you drain. That removes the waste that drives nitrate and algae, not just the water.
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FAQ
How often should I change aquarium water?
For most tanks, 20–30% weekly. Test your nitrates: if they climb above ~40 ppm between changes, do them more often or larger.