My chicks have been "bathing" in their shaving and spilled food! So I figured it was time to provide a sand bath. I made a tray (using a container that is about 8"x12"x3" Filled it will construction sand some DE and some ashes. A few are interested in it but they are mainly using it for a big grit cup! LOL. Anything special I should do with it? Do I leave it accessible all the time?