people have there own views on what size tank..some say 125 is the minimum and some say 300gal is the minimum..as far as the trigger, nope..the trigger will eat the sharks cartilage.
nothing too big..maybe a snowflake eel..or some smaller fish that the shark wont eat..from what i hear no puffers or triggers though..and if ur shark does outgrow the 125 it would take a while..search the agressive forum for more info