What do people use for dust baths? I have nothing but bermuda grass in my yard, no dirt. Can't have them free range. Have looked for sand in different stores, but the only thing I've found is concrete sand. Is that safe? Any dirt in the nursery section has fertilizer in it. any advice would be appreciated. My chicks are 21 weeks and have been laying since they were 17 weeks. Getting 5-6 eggs daily.