A premium square canister for tanks up to 160 gallons, with lots of media and thoughtful maintenance features.
Amazon $329.99
The flow king for very large tanks, at the lowest cost per rated gallon. Many owners pair it with a second filter on tanks near its rating.
- Up to 400 galTank size
- 925 gal/hFlow
- 5.9 LMedia
- 43 WPower
Price checked November 9, 2026. As an Amazon Associate we earn from qualifying purchases.
- 925 gal/h of flow for tanks up to 400 gallons
- Lowest price per rated gallon of the big filters
- Water-change valve and self-starting pump
- 5.9 L of media is little for a 400 gallon rating
- Large footprint, 15.75 in square
The Fluval FX Series family
Every Fluval FX Series model we rank, smallest first. Ratings compare each against its own tank size.
| Model | Tank size | Rating | Price |
|---|---|---|---|
| Fluval FX2 | Up to 175 gal | 3.2/5 | $296.99 |
| Fluval FX4 | Up to 250 gal | 3.4/5 | $337.99 |
| Fluval FX6 (this one) | Up to 400 gal | 3.4/5 | $406.99 |
How it scores
The rating comes from 6 measured or published factors, each scored 0-100 against fixed reference points for its tank size. How we rank explains each one.
Specifications
| Model number | A219 |
|---|---|
| Capacity | |
| Rated aquarium | Up to 400 gal |
| Pump output | 925 gal/h |
| Filter circulation | 563 gal/h |
| Turnover | 2.3x per hour |
| Max head height | 10.8 ft |
| Media | |
| Media volume | 5.9 L |
| Canister volume | 20 L |
| Features | |
| Primer | Yes |
| Shutoff valves | Yes |
| Built-in UV | No |
| Built-in heater | No |
| Water-change valve | Yes |
| Power and build | |
| Power draw | 43 W |
| Warranty | 3 years |
Alternatives in this tank size
A powerful, efficient filter for big tanks, with a handy water-change valve. Treat the 250 gallon rating as generous and size by media need.
Amazon $337.99A media-heavy filter for tanks up to 160 gallons, for owners who value biological capacity over raw flow.
Amazon $334.99Compare
Compare the Fluval FX6 with any other aquarium canister filter →
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