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
Up to 250 gal700 gal/h3.9 L
3.3/5
The most media in one canister here. On tanks near 225 gallons, add a powerhead for flow.
- Up to 225 galTank size
- 400 gal/hFlow
- 8 LMedia
- 25 WPower
Check price at Amazon$379.99
Price checked November 8, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- 8 L of media, the most here
- Pre-filter rinses on its own without opening the main canister
Cons
- Turnover is low for a 225 gallon rating
- 22 in tall, so check the cabinet height
The OASE BioMaster 2 family
Every OASE BioMaster 2 model we rank, smallest first. Ratings compare each against its own tank size.
| Model | Tank size | Rating | Price |
|---|---|---|---|
| OASE BioMaster 2 250 | Up to 70 gal | 3.7/5 | $229.99 |
| OASE BioMaster 2 350 | Up to 90 gal | 3.7/5 | $249.99 |
| OASE BioMaster 2 600 | Up to 160 gal | 3.3/5 | $334.99 |
| OASE BioMaster 2 850 (this one) | Up to 225 gal | 3.3/5 | $379.99 |
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 | BioMaster 2 850 |
|---|---|
| Capacity | |
| Rated aquarium | Up to 225 gal |
| Pump output | 400 gal/h |
| Turnover | 1.8x per hour |
| Max head height | 7.4 ft |
| Media | |
| Media volume | 8 L |
| Pre-filter volume | 0.7 L |
| Features | |
| Primer | Yes |
| Shutoff valves | Yes |
| Separate pre-filter | Yes |
| Adjustable flow | Yes |
| Built-in UV | No |
| Built-in heater | No |
| Water-change valve | No |
| Power and build | |
| Power draw | 25 W |
| Warranty | 3 years |
Alternatives in this tank size
OASE BioMaster 2 600
#4 in Over 150 galFull review
A media-heavy filter for tanks up to 160 gallons, for owners who value biological capacity over raw flow.
Amazon $334.99$334.99
Up to 160 gal350 gal/h6.8 L
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
Up to 175 gal475 gal/h3.9 L
Compare
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