Pest crab or good crab?

Found this little guy off my beach, thought he was an emerald crab underwater (red light doesn't do well at depth so he looked green). Not sure if he's a pest or not but he's pretty cool and I've been keeping him in my refugium for some time.

 

looks like an emerald but a photo of its pincers would tell us for certain, if the tips of the pincers are pointy they are used to grab, penetrate and hold prey... if they the tips are widened out, like spoons then they are used to grab and pull algae off the rocks and then...NOM NOM NOM!!!!!

all crabs pose a potential risk, if they go hungry they will adapt their diet and go for other tank inhabitants, otherwise emeralds are considered reef safe and useful algae controllers

 

Yeah I'm feeling pretty sure its a red minthrax crab, spoon like claws, and behavior like emerald crabs I've had before.