Pretty sure he just got the ban hammer. I won the bet it only took 13 minutes :rollface:
You won't have to worry about him anymore.
Getting back on track. I am not one to play tang police but don't put either of those guys in your 55. You would have to upgrade or trade them away once they got larger, and they do grow fairly quickly.
There are a bunch of fish you can go with that are nicely colored and exhibit the same grazing behavior. Dwarf Angels are a good choice. They have more of a tendency to nip clams than softies. Two dwarfs I have had good success with is the Cherub Angel and the Flame Angel. A buddy of mine also has a Coral Beauty that gives him no problems.
You would choose 1 of these for your tank as 2 together would probably fight till one died.
Again you can go with the tangs. But if you're going to have to move em out anyways, I'd go with something you can keep long term.
Also, if you go w/ a Yellow Tang try and buy them as a baby. A large majority of baby tangs come from Hawaii, where the capture methods are much more regulated than overseas. You won't have to worry about residual effects of cyanide (ie. a dead fish) in your new tang. I learned this from a guy who works for the local wholesaler who sells to all my LFS in the area.