Xanthid type Crab?

[Wingin It]

I caught this crab last night...he's probably a bit bigger than a toonie. What should I do with him? He's got red eyes, but not really hairy...is he likely the one eating some of my palys? Knocking on my glass at night? Is my reef 'healthier' with him in it? Or is he the one who's making some of my fish disappear?? All these questions...lol
Thanks!