In a 150 gal tank with some shelter, you picasso probably will not turn into a mad cow... I got one clown trigger (4 inch) with a ****** trigger (1 inch) with other fishes as Mac's angel (4 inch) , hippo tang (3 inches) , sailfin tang (3 inches) all holding theirselves in a 60 gal tank... just beware of not taking too long to add your other desirable fishes...because if left alone for a long time...picasso or any other marine fish , will become too territorial and may present trouble for your other fishes... usually one rule for triggers... add bigger fishes than the trigger and usually you will be fine...