I've never heard or read anywhere that eggshells can harm them. I've seen my torts eat pointy seeds, jagged pebbles, and eggshells. I'm no expert but they appear to be tough when it comes to eating these things. My torts actually seek out broken seed casings.Thank you all so much, I feel a lot better about it now. I'll just leave one in there and let them decide. And does anyone know about the egg shells being hard on them? Mine are only a few months old...