I use a tub of plain old dirt and I would keep that available to them even if I had other ideal dust bathing areas in my yard. Of course, our dirt here has a lot of sand in it already, but if yours doesn't you certainly could use sand. I don't think they care one way or the other as long as they can enjoy the dust bath. I also toss in a small scoop of food grade diatemateous earth (DE, in case I spelled that wrong again!) and mix that in. There are DE believers in the chicken world, and DE skeptics as well. I am thinking the reason for the DE is because it should help prevent mite infestations and such because it destroys those soft bodied insects. For me the jury is still out on prevention of parasitic worms so I don't add it to their food or water. I had it on hand before I got chickens because we had such a huge infestation of aphids on my flowers, but as a hummingbird freak I didn't want to use any pesticides. The plants looked a little dusty at first, but the aphids were almost gone after the second application. I figure if it worked that well to control those pesky little boogers it might be helpful against other soft bodied critters.
