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:

 

[Guygettnby]

I use fluval canister filters constantly. Nothing wrong with using them, but you do need to make sure you keep up with you cleaning and changing filters. I make sure it is rated for twice the size. My 40g has used a 407 for years and housed alot of corals.

For my larger tanks, I have always had one just incase of an issue that requires me to use extra carbon and filtration.

 

[vlangel]

I have an Oase BioMaster thermal 850 on my 75g and it is awesome. With live rubble rock in the baskets it has plenty of flow. The prefilter is very easy to remove and clean plus the integrated heater helps keep the tank equipment profile so clean looking. One caution: the prefilter is long so if the canister is under the tank, you will need to pull the canister away from under the tank. Mine is not, it is beside the tank behind an end table so that I can maintenance the canister right where it is at.