Emerald Crab

I have had my emerald crab for just over a month now. Last night i saw a very faded looking emeral crab, thought it was mine, almost floating off my live rock, i thought maybe it wasnt doing well and put it in a small "breeding tank thing that you would use for guppies and added some food for it. this morning i find that i have a very bright green emerald crab on the live rock near where i took the faded one from. I have to assume that he had shed and i put the exoskeleton into the breeding tank, my only question is is it possible for an emerald crab to shed its exoskeleton completely without destroying it,as i cant see any signs of exit on the faded crab skeleton, and the one still in my tank appears substantially larger. If this is not possible then i guess i must have gotten one in on the live rock and one of them died.

Thanks Erik

I originally bought him to comtrol some bubble algea. At first he was hiding alot, but now he will sit out in the open and climb on the rock and such. He is too small for me to worry about him getting any fish, but he might like to altho i have never heard of emeralds bothering fish. if you are interested you may want to look for a strawbery crab too, they are the same thing only a bright red instead of green. i would say that he is not the most active thing you could get for your tank, but it would be a cheaper addition for it.