Get chick grit. It's specially formulated for babies. The stones are pretty small, although there can still be a few larger stones mixed in that you may want to pick out as you don't want a chick to get impacted with too large a stone. Also use it sparingly, sprinkle it like you would pepper or salt. That's what I've been told anyway, and that's what I've been doing and my chicks are doing just fine. I did read that chicks don't regulate grit, like grown chickens do, so you may not want to let them free feed with it. I'm sure some people do with no problems, but I tend to be pretty cautious. I read that chicks don't need grit if they're eating commercially prepared chick starter only. Also I didn't give my chicks grit when they were just having a few bugs and egg yolk, but when I introduced spinach, I did give a little bit of grit so that they can grind that up in their little gizzards.