It is safer to give food grade to them in the dust or around the pen. If you want to mix it with their feed it NEEDS to be food grade. I ordered mine from here-
https://www.chewy.com/diatomaceousearth-food-grade-powder/dp/142396
I am not sure where you could find it in stores.
https://www.chewy.com/diatomaceousearth-food-grade-powder/dp/142396
I am not sure where you could find it in stores.