I recently got an Eheim ECCO canister and i love it, money well spent. The Rena XL (i think that's what it's called) also has a good reputation for being a great lower cost alternative to an Eheim. However when i went to buy my filter, the Renas were actually priced ~higher~ than the Eheims, and the Eheim came with their excellent biomedia plus the sponges, so i got the ECCO instead, and i don't regret it at all, it was very easy to set up and prime and after i completely disturbed my substrate during a replant, it cleared the water amazingly fast. The Eheim classic filters are almost universally regarded as the best there is, but that's probably overkill on a small tank like yours. My ECCO is the smallest one, it's rated up to 35 gallons, they have a couple larger sizes as well. Some people also really like Fluvals, but some people report problems with them, must be luck of the draw.
