I wouldn't keep them with smaller more subdued tetra's as the males tend to joust really fast up and down the length of the tank so it'd probably disturb smaller tetras. They'd be fine with Rams in my opinion but they are aggressive feeders. Gourami's, you could take a chance. Mine did give my butterfly fish a few nips when they noticed it but have since left it completely alone. As I said they can be a bit boisterous, and fast during feeding so it will come down to tank size.