I done the same thing and had good luck. My red leg hermit change shells like underware, as soon as they come across a new shell the change into it. I noticed as soon as they went into my tank a month ago they started doing it. Sometimes they get into a shell that is way to large pack it across the tank and then find a smaller one and trade it off. My blue leg hermits have been in the tank longer and are still sporting the shells I bought them with. Last week i noticed one of my red legged molesting my zoanthid, so I would tap on its shell to keep moving and then 3 days of doing this it was on top of the zoanthid and I went to move it and there was a snail attached to my zoanthid whick came out of the shell and took off and I thought I know that was a crab and looked and there was a crab still in there. Has anyone seen a crab and snail sharing the same shell?