I have 3 Melanistius in with my Betta, and they're great little fish, they come up and swim in the filter flow, flittering up and down in it, I admit sometimes I don't see them for a while as they hide in the plants, but when they come out they're great to watch. I have also just got 4 albino cory's as tank mates and they seem to take it in turns to zoom around in the filter flow. Corys are great fish!