View attachment 94755 I'm starting to really like sponge filters.
@Byron has noted that filters circulate the water as a benefit more than actually cleaning the water and that their home for beneficial bacteria is their greatest asset. Sponge filters will never trap fry or stop working mechanically due to a stuck impeller or some such thing. The dark color blends well and they are cheap to operate. No cartridges or anything else to buy. I'm using this one in a 20 gallon. It's big at 4" tall and 4.5 inches in diameter but I like it.