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In short
Most Whisper 20 to 60 filters take a Large Bio-Bag, the PF10 and 10i take a Medium, and the 3i takes a Small. The newer Whisper EX filters don't use Bio-Bags at all: they take Whisper EX carbon cartridges, Medium for the EX 20 and Large for the EX 30, 45 and 70.
Bio-Bag sizes
| Size | Filters Tetra lists |
|---|---|
| Small | Whisper 3i in-tank filter |
| Medium | Whisper PF10 power filter, 10i in-tank filter, Reptofilter 90 GPH |
| Large | Whisper 20, 30, 40 and 60 power filters; 20i and 40i in-tank filters |
Stay Clean Bio-Bag sizes
Tetra sells Stay Clean Bio-Bags for the same Whisper filters, and its page also lists the Whisper IQ models.
| Size | Filters Tetra lists |
|---|---|
| Medium | Whisper IQ 10, 10i, PF10 |
| Large | Whisper IQ 20, 30, 45 and 60; 20i and 40i; PF20, PF30, PF40 and PF60 |
Whisper EX carbon cartridges
| Size | Filters Tetra lists |
|---|---|
| Medium | Whisper EX 20 |
| Large | Whisper EX 30, EX 45, EX 70 |
If your filter says "EX" on the front, buy EX cartridges. A Bio-Bag is a different shape.
How often to change them
Tetra says to change Bio-Bags and EX cartridges monthly, or sooner if needed. For Bio-Bags it also says to rinse under cool tap water and replace when the flow drops. More detail is in how often to change an aquarium filter cartridge.
Leave the Bio-Scrubber in: Tetra's in-tank filter instructions say not to clean or replace the Bio-Foam or Bio-Scrubber unless it's damaged. That piece holds the helpful bacteria, so only the Bio-Bag gets swapped.
Not a Tetra filter?
Aqueon and Marineland use their own size letters. See the cartridge size chart for all three brands.
Questions people ask
What size Bio-Bag fits a Tetra Whisper 20?
Tetra lists the Large Bio-Bag for the Whisper 20, 30, 40 and 60 power filters and the 20i and 40i in-tank filters.
What is the difference between Bio-Bag and Stay Clean Bio-Bag?
Both fit the same Whisper filters, and Tetra's Stay Clean page also lists the Whisper IQ filters. Tetra sells the Stay Clean version as its upgraded Bio-Bag.
Which Tetra cartridge fits a Whisper EX 45?
The Large Whisper EX carbon cartridge. Tetra lists it for the EX 30, 45 and 70. The EX 20 takes the Medium.
Do I replace the Bio-Scrubber when I change the Bio-Bag?
No. Tetra's in-tank instructions say not to clean or replace the Bio-Foam or Bio-Scrubber unless it is damaged.
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.
