Ok, I think I understand well enough that the DE keeps things dry, keeps worms out of chickies guts, and keeps pests(fleas, mites, etc.) away. According to Perma-Guard's website, "Fossil Shell Flour" is the food grade DE. They also have a DE available for dusting pets it is labeled D-20. My question is, do I need them both or can the fossil shell flour do it all??? I'm getting my chicks form Murray McMurray and they also have 2 different DE's, one for ingestion and one for dusting. Just wondering what you all do? Thanks!