Well, IMO, it is a poor choice for a reef tank. That animal is not full grown, and they can wander and sting things very badly. If I were you, I would basically call that the 'main' animal in the tank, and not invest in alot of corals. And a spectacular animal it is, but it is also rather aggressive. In a 55, where there is not a lot of room to move, you may find it causing quite a bit of damage, either to other fish, or to corals. Really, even if a fish brushes past it, it can be badly stung.
This may be a situation where a good deal wasn't all that hot once more facts are known. Sorry 'bout that. I would seriously do some more research on these anemones, weigh your options, and take your chances.