Heh, I bought Mr. Tesla 5 guppies and 6 ghost shrimp a long time ago... He ate the ghost shrimp like it was turtle Christmas (which it was my intention for him to eat them), but he only ate 1 of the guppies and so far they have been chilling in his tank for a few months now. D:
They have babies, but I usually let them eat them (or Tesla does). They seem to nibble on his poop and the algae too, so I don't mind having them around as long as they don't multiply too much.

Some more fish would be cool, but I'm not sure if an "algae eater" fish would be good or not since apparently they poop a lot and Plecos can grow up to be b$%#!$%ds. Just watch for aggression depending on what type of fish it is.