DE is the skeletons of microscopic sea life (diatoms). It is used to control insects because, "The fine powder absorbs lipids from the waxy outer layer of insects' exoskeletons, causing them to dehydrate." (Wikipedia) Mostly harmless to birds and mammals except can cause very dry skin and certain forms with very sharp crystals are an inhalation hazard. Stall Dry is a mixture of DE and clay. I guess the DE keeps the parasites down while absorbing excess moisture, and the clay absorbs ammonia and odors, probably about as effective as kitty litter. Sweet PDZ, which I just learned about, is granulated or powdered zeolite, a mineral which naturally adsorbs (not absorbs) and breaks down ammonia. I really want to try it out in my chicken house, and more so in the smelly duck house. We used to keep fish in a 50 gallon aquarium and used zeolite rocks to control ammonia as well as filters loaded with activated charcoal and smaller zeolite chips, so I know that it works. Zeolite loaded with ammonia slowly releases nitrogen, which should make the old litter an even better fertilizer. Going to the co-op for feed tomorrow and I'll look for Sweet PDZ there.