My baby Mystery snails like egg shells in the snail jello I prepare for them. When a piece of eggshell is sticking up from the jello, I see two or three baby snails grazing on it. Like Msjinkzd said, you have to clean out the membrane from the shell; that gooey part which will pull off rather easily and will leave a clean surface that will feel just like the top of the eggshell.