If you want to catch him lean a glass in your tank on an angle so he can get it. Maybe near a rock face. Then put some shrimp in the cup, wait til morning and bins your uncle you should have a caught crab. If not repeat, you'll get him not sure if you have a sump but they are safe for sumps. Generally speaking

I have used crab traps in the ocean before with some raw chicken inside them and had good success.

also once you catch him you'll be able to get a really good look at him to see what he ooks like and to get a positive ID.

go to

http://chucksaddiction.com/hitchhikers.html

Thanks a lot guys. I dont have a refugium yet but next week it will be setup.

I actually went to the ID, it is under the Majoidea SuperFamily. It is on the last two of the various unknown species under that family.