My chooks' outdoor sand/dust pit gets frozen hard as a rock in the coldest part of winter. Even loose sand seems to get enough moisture in it to freeze hard. So my birds end up "bathing" in the shavings in their indoor coop, which I don't think really helps much to remove mites or lice. Sometimes I mix some fireplace wood ash or "sweet" (not hydrated/slaked) ground-up limestone powder in with those shavings, but I can't use much because I don't want my birds breathing the fine dust. DE is expensive and hard to get 'round here, so I haven't tried that as an option. What do you all do for your birds to provide a decent bug-removing dust bath in the winter, in cold climates? What works for you?