I bought the 'kids' a little pool that I intend to fill with whatever is best to use for them to dust bathe in. I plan on putting it in the open area underneath the coop to keep it out of the weather. I've been doing a lot of reading trying to learn what to use, besides just dirt. First I was gung ho about using DE, wood ash and fine sand and maybe some plain dirt. But I've read some negative things about using DE and wood ash and even the sand. What do you use? Recommend and why? Thank you.