I found the biggest fugly crab yet in my tank tonight!!!
It's black(Kind of looks a bit like a black scorpion colour.) with longer than usual legs, large pointy claws and when it's threatened it starts making a loud clicking (snapping) sound! (About half the volume of my large pistol shrimp.)
I tried catching it and only got one leg after moving about 40 lbs of rock around in the dark.
I have yet to see a crab that makes me squeemish, but this one does!
I'll try again in a couple of hours.
I'm shocked by this one. It's a little un-nerving.