Okay so I just let my 5 dwarf hermit crabs into my tank and right away one of the hermit crabs got out of its shell. I tried to nudge it back to him as he’s exploring the tank but he keeps leaving it. I do have extra shells but they are all bigger and he is quite small. I have no idea what to do and my local fish store said that there wasn’t much to do about it as they have a mind of their own.