Powder blus is asking for trouble for 2 reasons IMO. 1) they're very sensitive and ick magnets. 2) in such a small tank (less than 6ft), that tang will get stressed and turn into a super magnet.
If that new fish will eat others, I'd take him back and do the clown pair as was nicely suggested. Then, do a goby and blenny of your choice. Plenty to choose from.
You're not planning on a reef tank are you? Even still, a trigger will prevent you from keeping hermits, snail, or shrimp.