I keep my Bifas with a Regani, Melanurus, GT, Midas, clown loaches, and some rainbowfish without any problems. Mine aren't too aggressive, just make sure they can't swallow it. The Midas is the youngest and smallest of them all, but so far he's ok with everything. It's all going to depend on the temperament of your individual fish. I wouldn't try Amphs or Parachromis though in general if you want to be relatively safe though.