The short answer
Clean your filter media roughly once a month — and the golden rule: rinse it in old tank water, never under the tap. Tap water contains chlorine that instantly kills the beneficial bacteria living in your media, and those bacteria are the whole point of the filter. A gentle monthly rinse keeps flow strong without wrecking your biological filtration.
Why tank water, never tap
The sponges and ceramic media in your filter are coated in the bacteria that process fish waste. Chlorine in tap water kills them on contact. Rinse your media under the kitchen tap and you can crash your whole tank — a mini re-cycle with an ammonia spike that stresses or kills fish.
Instead, during a water change, scoop out a bucket of the tank water you’re removing and squeeze and swish the media in that. It removes the clogging gunk while leaving the bacteria alive.
How often, exactly
- Monthly is a good default for most tanks.
- More often if flow drops noticeably, the tank is heavily stocked, or the filter is undersized.
- Less often for lightly stocked or large tanks with plenty of media capacity.
Let flow rate be your guide: when the output visibly weakens, it’s time. Don’t clean on a rigid schedule if the filter is still flowing well — over-cleaning disturbs the bacteria needlessly.
Do it gently
- Only clean the mechanical parts (sponges, floss) regularly.
- Leave biological media (ceramic rings) mostly alone — a light rinse only when clogged.
- Never swap all the media at once; stagger replacements so the colony survives.
- Rinse the impeller while you’re in there to prevent noise.
For a full routine, see the aquarium maintenance schedule. If your filter is noisy, read why is my filter so loud, and never turn the filter off at night.