I have three cory's in a small tank all by themselves...and still seem to favor the back of the tank!
Ah, since I don't know how big your tank is...but if its big enough tiger barbs are good. Their an active fish, and I don't find them a "dirty" fish. But if you do put them in, think ahead, because you can't put other fishies (e.g. guppies) because they'll nip at their fins.
Caper