Thanks guys. I didn't mean to start a debate.
I used to sell DE when I managed a health food store years ago, it was FG 100% pure (not mixed like the feed store stuff) and was pure white. We used it on bugs and ants and it worked instantly.
It was never recommended to use internally though (even though it was food grade, to be used in kitchens around food and such). It was expensive as well (respectively, as you would use a tsp at a time).
The feed store stuff I bought is nothing like I remember the health food store stuff was, lol. It did work though! No more ants and flies are reduced... I'm not putting it in their food though.
Never had worm problems, nor fleas/mites.