Fluval FX6
#1 in Over 150 galFull review
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.
Amazon $406.99$406.99
The Fluval FX6 is the better aquarium canister filter overall, rated 3.4 to 3.3. The Fluval FX6 leads on value, efficiency and turnover. The OASE BioMaster 2 850 wins on media volume and features. The OASE BioMaster 2 850 costs $27 less ($379.99 vs $406.99).
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.
OASE BioMaster 2 850
#5 in Over 150 galFull review
The most media in one canister here. On tanks near 225 gallons, add a powerhead for flow.
Amazon $379.99$379.99
Which should you buy?
- Choose the Fluval FX6 for value ($1.02 per rated gallon ($406.99, up to 400 gal) vs $1.69 per rated gallon ($379.99, up to 225 gal)), efficiency (21.5 gal/h per watt (43 W) vs 16 gal/h per watt (25 W)) and turnover (925 gal/h for up to 400 gal, 2.3x per hour vs 400 gal/h for up to 225 gal, 1.8x per hour).
- Choose the OASE BioMaster 2 850 for media volume (8 L of media, 0.4 L per 10 rated gal vs 5.9 L of media, 0.1 L per 10 rated gal) and features (priming button or self-priming, shutoff valves, separate pre-filter, adjustable flow vs priming button or self-priming, shutoff valves, built-in UV, heater or water-change valve).
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 FX6 | OASE BioMaster 2 850 |
|---|---|---|
| Overall rating | 3.4/5 | 3.3/5 |
| Value 25% | 99 $1.02 per rated gallon ($406.99, up to 400 gal) | 71 $1.69 per rated gallon ($379.99, up to 225 gal) |
| Media volume 20% | 0 5.9 L of media, 0.1 L per 10 rated gal | 37 8 L of media, 0.4 L per 10 rated gal |
| Turnover 20% | 23 925 gal/h for up to 400 gal, 2.3x per hour | 8 400 gal/h for up to 225 gal, 1.8x per hour |
| Efficiency 10% | 97 21.5 gal/h per watt (43 W) | 62 16 gal/h per watt (25 W) |
| Features 15% | 70 priming button or self-priming, shutoff valves, built-in UV, heater or water-change valve | 85 priming button or self-priming, shutoff valves, separate pre-filter, adjustable flow |
| Warranty 10% | 50 3-year warranty | 50 3-year warranty |
Specifications
| Fluval FX6 | OASE BioMaster 2 850 | |
|---|---|---|
| Capacity | ||
| Rated aquarium | Up to 400 gal | Up to 225 gal |
| Pump output | 925 gal/h | 400 gal/h |
| Filter circulation | 563 gal/h | - |
| Turnover | 2.3x per hour | 1.8x per hour |
| Max head height | 10.8 ft | 7.4 ft |
| Media | ||
| Media volume | 5.9 L | 8 L |
| Pre-filter volume | - | 0.7 L |
| Canister volume | 20 L | - |
| Features | ||
| Primer | Yes | Yes |
| Shutoff valves | Yes | Yes |
| Separate pre-filter | - | Yes |
| Adjustable flow | - | Yes |
| Built-in UV | No | No |
| Built-in heater | No | No |
| Water-change valve | Yes | No |
| Power and build | ||
| Power draw | 43 W | 25 W |
| Warranty | 3 years | 3 years |