Ok not to worry I was just gonna say keep him in the sump .......sump Lord lol
Hopefully someone will be on soon to ID it for you
Does he's claws go into a point at the ends and does he have any hairs on he's body or legs
I say about the claws because some of the more friendly crabs have flat bits at the ends instead of points
Oh no he's not friendly I have 3 hermit crabs left out of 18, and 1 snail out of 5. Thank you blue legged crab for killing most. Tho karma bit him in the end, this big crab got him
To be on the safe side I'd flush him , it's cruel but at the end of the day you have gotta do what's best for your tank and haveing him in there isn't the best for your tank lol
That's a wild emerald crab. Well, at least that's my best guess. A clearer photo would help, one of the claw and one of the overall crab. But I'd wager it's an emerald based on the leg shape and the coloration.