Fluval Phosphate Cartridge G6
Water type
Freshwater + Marine
Fits
Fluval G6 Advanced Filtration System
Part no.
A420
Fluval Phosphate Cartridge G6
Drop-in phosphate media for the Fluval G6, sized for its larger media chamber. The Fluval G6 Phosphate Cartridge (A420) is a genuine replacement module for the G6 Advanced Filtration System, removing up to 3900 mg of phosphate ion from fresh or marine aquarium water before it can feed nuisance algae.
Key features
- Genuine Fluval A420 — the exact phosphate module engineered for the G6's stackable media chamber, not a generic pad cut to fit.
- Removes up to 3900 mg of phosphate ion — almost double the G3 cartridge's capacity, matching the G6's larger media stack.
- Fresh or marine — one cartridge works across both water types.
- Drop-in fit — slots straight into the G6's media stack alongside the pre-filter and biological stages, no cutting or soaking required.
Specifications
| Spec | Value |
|---|---|
| Manufacturer part number | A420 |
| Fits | Fluval G6 Advanced Filtration System |
| Phosphate removal capacity | Up to 3900 mg of phosphate ion |
| Water type | Freshwater and marine |
Fluval does not publish a stated service life in weeks or months for this cartridge — capacity depends on how much phosphate is in the water it's treating, so replacement is best guided by a phosphate test kit rather than the calendar. That figure is left off rather than guessed.
Not included
- The G6 Advanced Filter itself. This cartridge is a media module for the existing filter, not a standalone unit.
Suitable for, and not suitable for
Suitable for a Fluval G6 filter running elevated phosphate — visible as green or brown algae despite otherwise good water quality. Not a substitute for regular water changes, and it won't remove phosphate that's bound up in substrate or decor rather than dissolved in the water column.
Care and maintenance
Rinse the cartridge housing in tank water at each filter service to clear trapped debris, and retest phosphate levels with a test kit before assuming the cartridge still has capacity left — a saturated cartridge stops working with no visible sign.
Goes well with
- Fluval Pre Filter Cartridge G6 — protects this cartridge from clogging with debris.
- Fluval Fine Pre Filter Cartridge G6 — an extra polishing stage ahead of the phosphate media.
- Fluval Nitrate Cartridge G6 — pairs with phosphate removal for full nutrient control.
Warranty and delivery
Covered against manufacturing defects, in addition to your rights under Australian Consumer Law. Standard freight applies.
Common questions
How long does the G6 phosphate cartridge last?
It depends on how much phosphate is in the water, not a fixed number of weeks. Test regularly with a phosphate test kit and replace once readings start climbing again.
Does it work in a marine tank?
Yes, it's rated for both freshwater and marine use.
Will it fit the Fluval G3?
No — the G3 uses its own, smaller phosphate cartridge (A419) sized for its smaller media chamber.
Do I need to rinse it before use?
No rinsing is required before fitting; just drop it into the media stack as directed in the G6 manual.
