The local feed stores are out of chick grit. Does anyone have any DIY versions they recommend? I want to start offering my chicks small amounts of food other than their feed. I have some un-opened bags of playground sand that we haven't needed for my kids' sandbox....would that be too fine? Should I get some of our regular chicken grit and pound it down with a hammer? I plan to dig up a piece of grass w/soil and put in their brooder as well, but I doubt that would be sufficient. Anyone have any ideas?