where did i miss where he mentioned a 50gal tank?
when it comes to triggers and most fish for tha tmatter, you have to go by individual personalities. i have seen evil nigers and ones that get beaten up by flame angels (go figure) and i have seen the bite marks on a persons hand from a clown trigger, and well.... i have never seen a nice clown trigger, but you get the idea. watch the fish in the store for a while, believe me we are used to you guys staring at the tanks for hours. look at the fish's tankmates. are they torn to bits? do they show signs of illness? what about the trigger, is he beaten up, and if so by what? how does he act when fed, or when someone puts their hand in the tank. these are all vey important clues as to the personality of a fish.
if you want a trigger that has potential to play nice, dont buy the one following your finger, he is not being cute (ok maybe a little) he wants to eat your finger, and possible his tankmates too.
generally the nicer species are going to be niger, crosshatch, blue jaw, sargassum, pink tail etc.