My Salvini is the only fish in my tank that will challenge my jag. He's in there with a jag, umbee, midas, and festae. Maybe not the smartest fish, as his tail has a huge slit in it right now because he picks fights that he can't win, but he survives and never appears to be stressed much. If you're gonna keep one with less aggressive fish I'd make sure he's one of the smaller fish in the tank. If u got more aggressive fish that'll outgrow the Salvini, I'd probably make sure he's one of the bigger guys in your tank as he more than likely won't grow as fast.