Fluval Tri Ex Absorbing Cartridge G3
Suits tanks
150–300 L
Water type
Freshwater
Fits
Fluval G3 canister filter
Part no.
A423
Fluval Tri Ex Absorbing Cartridge G3
Handles three jobs in one cartridge slot on the Fluval G3. The Tri-EX cartridge combines activated carbon with phosphate- and nitrate-removing resin in a single unit, sized for the chemical media stage of the Fluval G3 canister filter (Fluval item A423). It tackles odour, discolouration and the two nutrients that drive algae growth in one pass, without needing three separate media baskets.
Will it fit my filter?
Yes, if you run a Fluval G3 canister filter. The G3 is rated for aquariums of 150-300 L (40-80 US gal). This cartridge is sized for the G3's media basket only — it does not fit the larger Fluval G6, which takes its own Tri-EX cartridge (item A424).
Key features
- Three media in one cartridge — activated carbon, phosphate-removing resin and nitrate-removing resin combined, so you're not running separate baskets for each.
- Purpose-built for the G3 — shaped to seat correctly in the G3's chemical stage, unlike generic universal carbon pads.
- Targets the causes of algae flare-ups — phosphate and nitrate removal addresses the nutrients that feed nuisance algae, not just the symptoms.
- Drop-in replacement — swaps in during a normal filter service, no cutting or repacking required.
Specifications
| Field | Details |
|---|---|
| Fits | Fluval G3 canister filter only — not compatible with the larger Fluval G6, which uses its own Tri-EX cartridge (item A424) |
| Manufacturer part number | A423 |
| Media type | Activated carbon, phosphate-removing resin and nitrate-removing resin combined in one 3-in-1 cartridge |
| Removes / provides | Phosphate, nitrate, organic waste, odour and discolouration |
| Water type | Freshwater |
| Replacement interval | Not published by Fluval — check water clarity and nitrate/phosphate test results every 4 to 6 weeks, and replace once readings stop improving after a water change |
Suitable for, and not suitable for
Suitable for freshwater aquariums running a Fluval G3. Not recommended for reef or invertebrate systems, where phosphate stripping needs to be more gradual and controllable — a dedicated reactor is the better tool there. It's not a substitute for the G3's separate mechanical and biological media, which still need their own regular servicing.
Care and maintenance
Fluval does not publish a fixed replacement interval for this cartridge. As a general guide, check water clarity and your nitrate/phosphate test results every 4 to 6 weeks, and replace the cartridge once readings stop improving after a water change.
Warranty and delivery
This is a consumable filter media, used until exhausted rather than covered under a mechanical warranty. Standard parcel delivery.
Common questions
Can I use this in a Fluval G6 instead of a G3?
No. The G6 takes its own Tri-EX cartridge, item A424, sized for its larger housing. The two aren't interchangeable.
Do I need a separate carbon cartridge as well?
No. This cartridge already includes activated carbon alongside the phosphate and nitrate resin, so a separate carbon cartridge isn't needed at the same time.
Will this affect phosphate dosing on a reef tank?
This cartridge is intended for freshwater use. On a reef tank, faster or less predictable phosphate stripping can undo deliberate dosing — a controllable reactor media is the better choice there.
