I hate the type of post I'm about to make, because it's such an atypical example. Therefore, a disclaimer--this is by no means the usual story for a PBT.
A customer of mine has had a PBT in her 125 or so tank for 2 years now. It's a 3' cube, and is housed with a bird wrasse and dogface puffer. All these fish were added before I got her as a customer. The odd thing is that she's never fed it nori, or any other type of algae. Just frozen Marine Cuisine cubes. There's no LR in the tank either. The strange thing is this fish looks great. No HLLE, no sunken belly, great colors...definitely a rarity with this fish. It's incredibly territorial as well.