Crabs alive. What the heck is it.

[Lynnzer]

This little crab was found in the tank when I lifted a few live rocks to clear aiptasia from them.
He's about 20mm across the shell which has a sort of curly wave across it in pale spots.
The claws aren't very big and both nippers are equal sizes. I'm guessing it's feeding on bottom detritus or I think it would have larger claws.
Any idea what it is, it's usefulness or otherwise in a reef tank, and how large could it grow to?

 

[michael_cb_125]

It looks very similar to the green crabs that we use for bait, lol. Probably not that species as green crabs are a cool water species. I would remove from the tank. While small he may not cause issues, but as he gains size this will change.
~Michael

 

[Lynnzer]

It looks very similar to the green crabs that we use for bait, lol. Probably not that species as green crabs are a cool water species. I would remove from the tank. While small he may not cause issues, but as he gains size this will change.
~Michael

You're right. It is a green crab. How in hell it got there I'll never know but it's about to become a meal for my anemones

 

[kjkszpj9]

That literally looks like what i would catch when i was a kid in Sweden lol.