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
The OASE BioMaster 2 850 is the better aquarium canister filter overall, rated 3.3 to 3.2. The OASE BioMaster 2 850 leads on media volume and features. The Fluval FX2 wins on turnover and efficiency. The Fluval FX2 costs $83 less ($296.99 vs $379.99).
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 OASE BioMaster 2 850 for media volume (8 L of media, 0.4 L per 10 rated gal vs 3.9 L of media, 0.2 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).
- Choose the Fluval FX2 for turnover (475 gal/h for up to 175 gal, 2.7x per hour vs 400 gal/h for up to 225 gal, 1.8x per hour) and efficiency (17.6 gal/h per watt (27 W) vs 16 gal/h per watt (25 W)).
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 | OASE BioMaster 2 850 | Fluval FX2 |
|---|---|---|
| Overall rating | 3.3/5 | 3.2/5 |
| Value 25% | 71 $1.69 per rated gallon ($379.99, up to 225 gal) | 70 $1.70 per rated gallon ($296.99, up to 175 gal) |
| Media volume 20% | 37 8 L of media, 0.4 L per 10 rated gal | 13 3.9 L of media, 0.2 L per 10 rated gal |
| Turnover 20% | 8 400 gal/h for up to 225 gal, 1.8x per hour | 35 475 gal/h for up to 175 gal, 2.7x per hour |
| Efficiency 10% | 62 16 gal/h per watt (25 W) | 72 17.6 gal/h per watt (27 W) |
| Features 15% | 85 priming button or self-priming, shutoff valves, separate pre-filter, adjustable flow | 55 priming button or self-priming, shutoff valves |
| Warranty 10% | 50 3-year warranty | 50 3-year warranty |
Specifications
| OASE BioMaster 2 850 | Fluval FX2 | |
|---|---|---|
| Capacity | ||
| Rated aquarium | Up to 225 gal | Up to 175 gal |
| Pump output | 400 gal/h | 475 gal/h |
| Filter circulation | - | 343 gal/h |
| Turnover | 1.8x per hour | 2.7x per hour |
| Max head height | 7.4 ft | 6.9 ft |
| Media | ||
| Media volume | 8 L | 3.9 L |
| Pre-filter volume | 0.7 L | - |
| Canister volume | - | 10.6 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 | No | No |
| Power and build | ||
| Power draw | 25 W | 27 W |
| Warranty | 3 years | 3 years |