Fluval FX4
#3 in Over 150 galFull review
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 $337.99$337.99
The Fluval FX4 is the better aquarium canister filter overall, rated 3.4 to 3.2. The Fluval FX4 leads on value, efficiency and features. The Fluval FX2 wins on media volume. The Fluval FX2 costs $41 less ($296.99 vs $337.99).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
Fluval FX2
#6 in Over 150 galFull review
A compact high-flow canister for large tanks. Its media space is modest for the rating, so it suits tanks well under 175 gallons best.
Amazon $296.99$296.99
Which should you buy?
- Choose the Fluval FX4 for value ($1.35 per rated gallon ($337.99, up to 250 gal) vs $1.70 per rated gallon ($296.99, up to 175 gal)), efficiency (23.3 gal/h per watt (30 W) vs 17.6 gal/h per watt (27 W)) and features (priming button or self-priming, shutoff valves, built-in UV, heater or water-change valve vs priming button or self-priming, shutoff valves).
- Choose the Fluval FX2 for media volume (3.9 L of media, 0.2 L per 10 rated gal vs 3.9 L of media, 0.2 L per 10 rated gal).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every over 150 gal aquarium canister filter; a clear win is highlighted. How we rank explains each one.
| Factor weight | Fluval FX4 | Fluval FX2 |
|---|---|---|
| Overall rating | 3.4/5 | 3.2/5 |
| Value 25% | 83 $1.35 per rated gallon ($337.99, up to 250 gal) | 70 $1.70 per rated gallon ($296.99, up to 175 gal) |
| Media volume 20% | 1 3.9 L of media, 0.2 L per 10 rated gal | 13 3.9 L of media, 0.2 L per 10 rated gal |
| Turnover 20% | 37 700 gal/h for up to 250 gal, 2.8x per hour | 35 475 gal/h for up to 175 gal, 2.7x per hour |
| Efficiency 10% | 100 23.3 gal/h per watt (30 W) | 72 17.6 gal/h per watt (27 W) |
| Features 15% | 70 priming button or self-priming, shutoff valves, built-in UV, heater or water-change valve | 55 priming button or self-priming, shutoff valves |
| Warranty 10% | 50 3-year warranty | 50 3-year warranty |
Specifications
| Fluval FX4 | Fluval FX2 | |
|---|---|---|
| Capacity | ||
| Rated aquarium | Up to 250 gal | Up to 175 gal |
| Pump output | 700 gal/h | 475 gal/h |
| Filter circulation | 450 gal/h | 343 gal/h |
| Turnover | 2.8x per hour | 2.7x per hour |
| Max head height | 6.9 ft | 6.9 ft |
| Media | ||
| Media volume | 3.9 L | 3.9 L |
| Canister volume | 14 L | 10.6 L |
| Features | ||
| Primer | Yes | Yes |
| Shutoff valves | Yes | Yes |
| Built-in UV | No | No |
| Built-in heater | No | No |
| Water-change valve | Yes | No |
| Power and build | ||
| Power draw | 30 W | 27 W |
| Warranty | 3 years | 3 years |