A better option is Diatomaceous earth. It's crushed seashells you can buy it at any Pool Supply and it's non-toxic and it'super fine. I have used it many times. I even put it on my dogs and in their on their bedding can be used in fish tanks in your yard it's all natural non-toxic.i would Check into that. As far as the egg shells I'm not sure about that one. Hope that helps.