Fluval CHI Aquarium Foam Pad Replacement
Fits
Fluval CHI 5 US Gal (19 L), model 10505, Fluval CHI II 5 US Gal (19 L), model 10505
Part no.
A1421
Replace every
2 months
Fluval CHI Aquarium Foam Pad Replacement
The coarse stage that keeps a Fluval CHI's filter cube working properly. This is the genuine foam pad — the coarser mechanical and biological stage of the CHI's concealed filter cube — sized for the Fluval CHI and Fluval CHI II 5 US gallon (19 L) aquarium kit, model 10505.
Key features
- Genuine Fluval part A1421 — the coarse foam element of the CHI's two-stage filter cube.
- Catches larger debris and gives beneficial filter bacteria somewhere to colonise.
- Longer service life than the filter pad — built to run around 2–3 months between full changes.
- Works alongside the filter pad — together they form the CHI's dual-stage mechanical filter (filter pad sold separately).
Specifications
| Part number | A1421 |
|---|---|
| Fits | Fluval CHI & Fluval CHI II, 5 US gal (19 L), model 10505 |
| Filtration stage | Mechanical and biological — coarse debris plus bacteria colonisation |
| Recommended replacement | Every 2–3 months |
Will it fit my filter?
Check your CHI is the 5 US gallon (19 L) model 10505 — the compact bowl-style kit with a rotating top filter cube, sold as both the original Fluval CHI and the later Fluval CHI II. We haven't been able to confirm this pad also fits the larger 25 L (6.6 US gal) Fluval CHI II, model 10508 — check your filter cube size before ordering if you have that model, or get in touch and we'll help confirm.
Suitable for, and not suitable for
Suitable for routine servicing of the 5 US gallon (19 L) CHI or CHI II. This listing is the foam pad only — it isn't a substitute for the finer filter pad, which handles a different filtration stage and is sold separately.
Care and maintenance
Fluval's care guide calls for a full foam pad replacement around every 2–3 months. Between full changes, a gentle rinse in removed tank water — not tap water — clears trapped debris without stripping out all of the bacteria it's carrying.
Common questions
How often should I replace the Fluval CHI foam pad?
Around every 2–3 months under normal stocking, per Fluval's care guide — sooner in a heavily stocked tank.
Can I just rinse it instead of replacing it?
A gentle rinse in tank water between changes is fine and protects the bacteria colony, but the foam still needs full replacement periodically as it compacts and degrades.
Will this fit the larger 25 L Fluval CHI II?
This listing is sized for the 5 US gallon (19 L) CHI and CHI II, model 10505. We haven't confirmed fitment on the larger 25 L (6.6 US gal) model 10508 — check your filter cube against the pad before ordering.
Warranty and delivery
Covered by your rights under Australian Consumer Law, in addition to Fluval's standard parts warranty against manufacturing defects. Small, lightweight item — standard parcel delivery Australia-wide.
