I have one, and he eats mysis like a pig (although you should never buy one without seeing it eat with your own eyes, because not all will eat), but I also have a feeling he's slowly turning my snails into midnight snacks. Be careful of longer nosed tangs. I have a kole (who was added after the cbb, same size and looks nothing like the cbb), and they did fight a little at first. They're ok now, but you may run into bigger trouble with any species that might look more like a butterfly to the CBB. They also like a lot of LR to pick through, and IME they don't eat a whole lot at once (mine eats a few PE Mysis a day, and possibly a snail for snack at night), so you may have to feed them more often than your other fish.
If your only reason for wanting one is for it to eat aiptasia, I'd say don't get one. I got mine just because I've always loved CBB's. Not all CBB's will eat aiptasia (it's 50/50), and with them being a pretty delicate fish, I think there are better options for fighting off pest nems. Have you tried aiptasia-x, kalk paste?