Choosing a Canister Filter for 55-gal Saltwater — OASE Biomaster Thermo 600 vs EHEIM Classic

[Andrés Garza]

Hello Reefers,

I have a 55-gallon (≈200 L) saltwater aquarium (fish-only) and I am evaluating external canister filters. My shortlist:

• OASE Biomaster Thermo 600
• EHEIM Classic (92-gallon rated)
• Also considering: Fluval 407, Penn Plax Cascade 1200, and SunSun (though I find fewer reviews for these).

I’d appreciate your technical feedback and real-world experience, especially if you’ve used any of these in a marine setup.

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What I’d like to know:

1. Actual flow vs rated flow: Does the model maintain its advertised flow after adding media and hoses? Any noticeable flow loss over time due to airlocks or impeller wear?

2. Media volume & layout: How many liters or baskets does each canister hold? How easy is it to customize media (bio / chem / mechanical)?

3. Prefilter or mechanical stage: Is there a removable prefilter that can be cleaned without opening the entire canister (like the OASE tube-style prefilter)?

4. Priming and air handling: How reliable is the self-priming? Any issues with trapped air, gurgling, or needing to re-prime frequently?

5. Materials & saltwater compatibility: Any corrosion problems (metal clips, springs, seals) or plastic parts that degrade in marine conditions?

6. Noise & vibration: Subjective impressions or noise comparisons between these models.

7. Maintenance ergonomics: How easy is disassembly, cleaning the impeller, replacing seals, etc.? How long does a typical maintenance take?

8. Longevity & reliability: How long have yours lasted? Any recurring issues (impeller shaft, motor, o-rings)? Are spare parts easy to find?

9. Performance in marine systems: If you’ve used them on fish-only or reef setups, was the flow adequate or too strong/weak for certain livestock?

10. General recommendation: For a 55-gal saltwater aquarium, would you choose a filter rated near that volume or oversize it? By how much?

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My main decision is between the OASE Biomaster Thermo 600 and the EHEIM Classic (92-gallon rated), but I’m open to input on the Fluval 407, Penn Plax Cascade 1200, and SunSun.

Thanks in advance for sharing yo
ur experiences and technical feedback!

 

[SantaMonica]

Generally, you don't want a canister for a reef

 

[kharmaguru]

I'm using a sunsun hw3000 on a 40 breeder frag tank. It has a split output and I have two RFGs on it that do a great job creating turbulent wave motion. I have it entirely filled with fluvial bio-fx media. This really needs a prefilter but I have yet to find something with large enough connections for 22mm ID hose. I only clean it once every 6 months and the flow stays strong. I have everything integrated into an undrilled overflow - filter intake, heater, ATO. You can do this with any canister however if you are not doing a similar undrilled overflow then that leads to my recommendation - get the Oase because of the integrated prefilter and heater compartment.

Here's a guy running an SPS reef tank on an Oase filter: