I have put small hermit crabs that I found in the tidepools in my tank before, they all died. They looked pretty close to the zebra hermit, so i figured they were safe, and they just died. I also got another from the beach that was huge like 2 inches, but I looked it up and it wasnt reef safe, so i gave it to my friend who has an agressive tank. I would say if you can recognize the hermit, thats fine. But otherwise I wouldn't really put your tank at risk for disease or anything like that.