Those crabs probably came in as hitchikers on Florida aquacultured LR. They resemble emerald crabs, but with a red color. A good way to know if it is predatory is to look at the claws, does it have sharp points or pads like an emerald? Anyway, that one has pads, not points, but I have witnessed the ones I have eating corals too. However, every emerald crab I have had has also picked on corals. IMO, it is just a gamble. Some of those crabs will cause problems while others won't. If you aren't seeing any damage to any corals, I say give it the benefit of the doubt.
You have lots of good looking corals in there. Hope that long tentacle plate keeping doing well for you.