Internal Corner Filter

I have used those, just the same principle as a box filter except layered...they work fine. They are a pain to clean, I honestly never clean them, but I just use them for fry, quarantine, hospital, grow out tanks and such.

If you don't plan on using chemical media, I'd say go with a sponge filter since it's so much easier to clean. It will provide mechanical and biological filtration, probably just as well if not better than this corner filter.
 
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