mickster, many bad things here..
A: Taking hermit crabs off shores is illegal, unless otherwise posted. It is called poaching, and you can be fined for it, or arrested if you do it on a larger scale
B: Afraid of a more painful death? Of course, that's what nature is. Would you rather have it die in one quick swipe in nature, or die a slow, painful, aggonizing death in your tank, with the wrong conditions?
Animals have things called "instincts" that teach them what to do. They are born with them. They know how to live in their own home. You taking them out of nature is putting them in a weird place, and they have no idea how to live like that.
Think about it.. do the right thing
