This is exactly why I love BYC. I had seen 1 or 2 people using sand in the coop and one referred to it as "playground sand." I went and got enough to cover my coop and run and I absolutly love it. The birds weren't quite sure waht to think at first, but now they really enjoy it. I don't give mine and grit, but under the thin layer of sand there is plenty of soil with small rocks, about the size of commercial girt. I have done the sand in the brooder box, and it worked well. it will hold the heat and i was actually having to turn the light off every so often because it was to warm. so just keep an eye on them, or use a thermometer with an alarm like the one I have. I don't remember the brand but I got it at Lowe's for about $20. Until i put sand in the brooder I'd never seen a chick take a dirt bath.