We have added a nice 10xx10 covered chain link yard for the girls to hang out in during the day. They scratch and sometimes create a nice divit to lay in and roll around in. I know dust bathing is crucial for mite control. The ground in here is hardish so should I provide a big bowl area filled with maybe play sand for them to dust in or is there a better product to provide in that big low bowl? I have DE that I sprinkle in the yard but should I just fill the bowl with that alone?