The short answer
A loud filter almost always comes down to one of three things: trapped air, a low water level, or grit or debris in the impeller. All three are easy to diagnose and fix. A healthy filter should hum quietly with a soft trickle — rattling, gurgling or grinding means something needs attention.
The usual culprits
Trapped air. Air pockets inside a canister or internal filter make a gurgling, sputtering sound. Gently tilt or shake the filter (or the canister) to release the bubbles, and they’ll work their way out.
Low water level. If the water has dropped from evaporation, the outflow splashes and the intake may suck air, causing a loud gurgle. Top the tank up and the noise usually vanishes.
Grit in the impeller. The impeller is the small spinning magnet that drives the flow. A stray bit of gravel, sand or gunk makes it rattle or grind. This is the most common cause of a persistent buzzing filter.
How to quiet it down
Work through these in order:
- Top up the water to the correct level.
- Burp the air out by tilting the filter.
- Clean the impeller and its slot — the number-one fix.
- Rinse clogged media so flow isn’t restricted (in tank water, never tap).
- Check it’s seated properly and cushioned — vibration against the glass amplifies sound.
If the impeller is worn or cracked, a cheap replacement part usually silences an older filter.
When to look deeper
A filter that stays loud after all this may be undersized, aging, or clogged internally. A regular clean prevents most noise in the first place — see how often to clean your filter. If you’re due an upgrade, browse the filters hub, or our best external and best internal picks.