A hand lifts a dripping white filter cartridge out of a hang-on-back filter on a planted fish tank

Aquarium filters

Which aquarium filter cartridge fits my filter?

Updated Oct 25, 2026
7 sources

Buy links on this page go through our /go/ redirects to the manufacturer or retailer. We earn nothing from them today; that may change. Disclosure.

Quick answer

Filter cartridges aren't universal. Tetra, Aqueon and Marineland each size cartridges for their own filters, and a "Large" from one brand won't fit another brand's Large slot. Find the model number on your filter or its box, then match it in the charts below.

Replacement cartridges by brand:

Tetra Whisper Bio-Bag Aqueon cartridges Marineland Rite-Size A, B, C

Fit lists from Tetra, Aqueon and Marineland product pages. Sizes are not interchangeable across brands.

Match the cartridge to the filter

Brand and size	Filters the maker lists	Change every
Tetra Whisper Bio-Bag, Small	Whisper 3i in-tank	Monthly, or sooner
Tetra Whisper Bio-Bag, Medium	Whisper PF10, 10i, Reptofilter 90 GPH	Monthly, or sooner
Tetra Whisper Bio-Bag, Large	Whisper 20, 30, 40 and 60 power filters; 20i and 40i	Monthly, or sooner
Tetra Whisper EX carbon, Medium / Large	EX 20 / EX 30, 45 and 70	Monthly, or sooner
Aqueon X-Small	E Internal Size 3	About every 4 weeks
Aqueon Small	E Internal 10; MiniBow 1, 2.5 and 5	About every 4 weeks
Aqueon Medium	QuietFlow LED PRO 10, Power Filter 10, E Internal 20	About every 4 weeks
Aqueon Large	QuietFlow LED PRO 20, 30, 50 and 75; Power Filter 20, 30, 50 and 55/75; E Internal 40; Canister 200, 300 and 400	About every 4 weeks
Marineland Rite-Size A	Penguin 100B, Mini, 99B	Every 2 to 4 weeks
Marineland Rite-Size B	Penguin 150B, 110B, 125B	Every 2 to 4 weeks
Marineland Rite-Size C	Penguin 200B, 350B, 170B, 330B	Every 2 to 4 weeks

Fit lists change as makers update their filters, so if your model isn't in the row you expect, check the maker's page linked under Sources. Aqueon makes this easy on its internal filters: the instructions say the cartridge size is printed on the underside of the lid.

Tetra: Bio-Bag, Stay Clean or EX?

Most Tetra Whisper power and in-tank filters take Bio-Bags. Tetra also sells Stay Clean Bio-Bags for the same filters, and its Stay Clean page adds the Whisper IQ models. The newer Whisper EX filters are different: they take Whisper EX carbon cartridges, Medium for the EX 20 and Large for the EX 30, 45 and 70. There's a full chart in Tetra Whisper cartridge sizes.

Aqueon: four sizes, one direction

Aqueon sells X-Small, Small, Medium and Large cartridges. Its page says to rinse a new cartridge under cold water and slide it in with the tab marked FRONT facing the front of the filter. Aqueon's internal filters also have a bio holster; the instructions say to rinse it in aquarium water, not tap water, and not to throw it away.

Marineland Penguin: A, B or C

Penguin Bio-Wheel filters take Rite-Size cartridges in three sizes, matched to the filter's model number. Marineland's manual says to replace the cartridge every 2 to 4 weeks and never to clean or replace the Bio-Wheel, because the color on it is the helpful bacteria.

Keep the bacteria: the makers keep one part out of the monthly swap on purpose: Marineland's Bio-Wheel, Tetra's Bio-Scrubber or Bio-Foam in the in-tank filters, and Aqueon's bio holster. Change the cartridge, but leave those in place.

Next steps

How we work: fit lists, sizes and intervals on this page come from Tetra, Aqueon and Marineland product pages and manuals, listed below. We have not tested these cartridges ourselves.

Questions people ask

Are aquarium filter cartridges universal?

No. Tetra, Aqueon and Marineland each size their cartridges for their own filters, and the size letters don't match across brands. A Tetra Large and an Aqueon Large are different shapes. Match the cartridge to your filter's model number.

How do I find out which size cartridge my filter takes?

Find the model number on the filter or its box, then look it up in the maker's fit list. Aqueon says its internal filters show the cartridge size on the underside of the lid.

Do Tetra Whisper EX filters use Bio-Bags?

No. Tetra sells separate Whisper EX carbon cartridges: Medium for the EX 20 and Large for the EX 30, 45 and 70. Bio-Bags are for the Whisper power and in-tank filters.

Which Marineland Rite-Size cartridge fits my Penguin filter?

Marineland lists size A for the Penguin 100B, Mini and 99B, size B for the 150B, 110B and 125B, and size C for the 200B, 350B, 170B and 330B.

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.