So I have an arrow crab in my 55, came home the other night to find one of his front claw arms had fallen off. Not sure how this happened? Is it normal? Do they regenerate? Or is something wrong with this guy? Any answers would be greatly appreciated.

Hello Whitevillian! Loss of appendages (arms or legs) on crabs can be caused by several different things and are not necessarily life threatening as long as this crab can defend himself and feed himself. He will be at a disadvantage of course with the loss, so you want to make sure that he has the means to make up for his temporary handicaps. Crab are capable of regenerating these lost appendages over time.

You will be truly amazed. One day it will appear and you will not have seen it coming. How do they do that?

God (nature, Gaea or whatever you want to call it) is amazing.

well i woke up this morning and flipped on the lights only to find the my arrow crab is now in pieces, I feel so bad. Not sure who could of done this to him. I think it is the emerald crabs in the tank, are they aggressive enough to do that to an arrow crab 4 times their size. Anyone?

I am sorry to hear that. I have not kept either species so I can't speculate.

I had an arrow crab a while back. I bought one to decimate my bristle worm population, they were everywhere. It was a lot of fun watching him pull them from the rock and then pull them apart. Everything was great till i turned on the lights one morning and he was dragging away my scooter blenny.:o