Dats and bichers are a good combo. The bichers will help clean up the bottom of uneaten food. I havent seen any aggression between mine. As for Fei fengs, dats and fengs are perfect for each other. Remember the trinity, Wide bar, asian aro, fei feng= dragon, tiger, phoenix. If anything just keep an eye on the feng because they have a tendency to suck the slime off other fish.