Help- I just bought 40 pounds of DE at the feed store. I asked them (several times) if it was food grade and I could use it for my chickens. I just don't know if it really is or not Nowhere on the bag does it say "food grade". There is a picture of poultry on it, as well as other livestock. The ingredients list DE and calcium carbonate. There isn't a suggestion of pool use on it. But it is gray, not white. Can I use it?? Will it kill my chickens?