The number of species of Plecs and Corys and other bottom feeders and algae eaters is enormous. I know there are entire sites out there like plecoplanet and plenty of others where extensive catalogs can be seen. We have any number of experts here on TFF who you can run across, but of course you sometimes have to have patience and gather a number of opinions.
A couple of pointers you may already know about: Being quite sure about the identity of the fish being purchased so that you definately understand what maximum size it might get to is of crucial importance. It's extremely easy to run across Plecs that can outgrow virtually any tank, even very large ones. Obviously a 55g will give you more possibilities, but you still have to be careful. Secondly, it's important not to generalize about these categories of fish getting their food from cleaning up the bottom or solely from algae. Each species must be understood individually and there may be rather unique dietary needs (sometimes wood is required, many need to be fed with wafers of various compositions, some of the algae eaters eat only certain types of algae and supplying it can be quite a feat - in fact sometimes one winds up realizing that certain of these fish are quite the opposite of something you throw in to clean up!)
Anyway, I'm not an expert but these are a few bits I've gathered from reading here at TFF. (By the way, using the search tool on this site is a powerful starting point for all sorts of learning.) Good luck with your research!
~~waterdrop~~
