I'll throw in my two cents...bamboo shrimp. Doesn't do much for algea, but picks through the gravel and is a filter feeder. I haven't been able to find much info on these, so I can only go off what I've seen in my own tank. They don't have a pincer...at least not big enough to hold a fish, so they're good in a community I think. The guy at the store said they would actually clean the fish...assuming the fish would hold still...this I have not witnessed. They're kinda shy, but kinda active. They're good at getting out of the tank, so a tight lid is a good idea.
