I don't think they eat corals but they are known to perch on them and can cause them to close up when they do so or get stung by it. I typically see them in smaller systems where they can be seen easily, aren't you setting up a 75g? Or is this for a nano?
The personality of a frogfish is that of a stomach that happens to occasional swim. Kidding aside, they are very sedentary, so don't expect an active fish. They won't eat corals, but can cause other problems as Grins pointed out.