Plan carefully b4 u setup ur tank, best to introduce smaller fishes in the first stage then come to the biger one... If is a fowlr setup then jus off ur lighting for a few days when u introduce new fishes, this will slow down their activities n gives new fishes less exposure to other fishes... Well, u may still c some agression here n there, don't worries, jus away fr ur tank or else u will kanna distress also. fishes r very smart like man also, they know how to gain for survival, they know when to test on u n when they can take advantage to swim further... of course, man should know them well n help them to gain higher chance of survival. fish-talk! Jus sharing my 2cents.