How Often to Change an Aquarium Filter Cartridge

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In short

About once a month. Tetra says to change Whisper Bio-Bags and EX cartridges monthly or sooner if needed. Aqueon says about every 4 weeks. Marineland's Penguin manual says every 2 to 4 weeks. All three say to change sooner if the flow slows down.

Time for a new one?

Tetra Whisper Bio-Bags Aqueon cartridges Marineland Rite-Size

Intervals from Tetra and Aqueon product pages and the Marineland Penguin manual.

What each maker says

Filter	Cartridge	Interval the maker gives
Tetra Whisper	Bio-Bag (S, M, L)	Monthly, or sooner if needed. Replace when the flow drops.
Tetra Whisper EX	EX carbon (M, L)	Monthly, or sooner if needed
Aqueon QuietFlow, Power and E Internal	Replacement cartridge (XS to L)	About every 4 weeks
Marineland Penguin	Rite-Size (A, B, C)	Every 2 to 4 weeks

Signs it's due sooner

The flow is weak. Tetra says to replace the Bio-Bag when the flow drops.
The light is blinking. Aqueon's QuietFlow LED PRO manual says the LED flashes when the cartridge is clogged and water is rising inside the filter.
Water is going over the top of the cartridge. On hang-on-back filters, a clogged pad makes water spill over it instead of through it, which is what Aqueon's light is warning about.

Rinse or replace?

Tetra says to rinse a Bio-Bag under cool tap water, then replace it when the flow drops. Aqueon is stricter about its bio holster: rinse it in water taken from the aquarium, not tap water, and don't throw it away. A rinse can buy time between changes, but the carbon inside a cartridge isn't something you can rinse back to new, which is why the makers give a monthly swap.

Parts you should not replace

Each brand keeps one piece out of the monthly swap because it holds the helpful bacteria:

Marineland Bio-Wheel: the Penguin manual says never to clean or replace it. A brown color on it is the bacteria doing its job.
Tetra Bio-Foam and Bio-Scrubber (in-tank Whisper filters): Tetra's instructions say not to clean or replace them unless they're damaged.
Aqueon bio holster: rinse in tank water only and keep it.

Change it the easy way

Unplug the filter.
Lift out the old cartridge over a bucket so the gunk doesn't drip back into the tank.
Rinse the new cartridge under cold water to wash off loose carbon dust (Aqueon's instruction).
Slide it in the right way round. On Aqueon, the FRONT tab faces the front.
Top up the tank if needed, plug the filter back in and check that water is flowing. If it isn't, see filter not working after a cartridge change.

Monthly cost: cartridges come in multi-packs, so one pack usually covers several months. Check the count on the box against the interval for your filter.

Questions people ask

How often should you change an aquarium filter cartridge?

Tetra and Aqueon both say about once a month, or every 4 weeks. Marineland's Penguin manual says every 2 to 4 weeks. All three say sooner if the flow drops.

Can I rinse an aquarium filter cartridge instead of replacing it?

Tetra says to rinse a Bio-Bag under cool tap water and replace it when the flow drops. Aqueon says to rinse its bio holster in aquarium water, not tap water, and not to throw the holster away.

Should I replace the Bio-Wheel or bio sponge too?

No. Marineland says never to clean or replace the Bio-Wheel, and Tetra's in-tank instructions say not to clean or replace the Bio-Foam or Bio-Scrubber unless it is damaged. They hold the helpful bacteria.

Why does my Aqueon filter light blink?

Aqueon's QuietFlow LED PRO manual says the light flashes when the cartridge is clogged and water is rising inside the filter. That means it's time to change the cartridge.

Sources

Last checked Oct 25, 2026. Fit lists and change intervals come from Tetra, Aqueon and Marineland product pages and filter manuals. Unplug the filter before you reach into it.