Algae eaters are good because they aren't just algae eaters. They eat any uneaten food that your fish miss and any algae or whatever that grows in the tank. A general 'clean up crew'. The most common and best all-around (in my opinion/experience anyways) one would be the bristle nose catfish. It doesn't grow too big for most aquaria, eats algae all through it's life cycle (which some don't), gets along with most anything and will get any uneaten stuff that floats to the bottom. The only down side to them, if there is any, is that they're not particularly colourful and some people find the male's bristles/mustaches unsightly. I'm not one of those people though and you can get golden versions of them that're more colourful but also usually more expensive.
Normal Bristlenose
Golden