The first week standard size chicks do good at half a square foot per chick. They will out grow it then and will need 1 square foot per chick for the next 2 weeks. Then add an addition half a square foot for every 2 weeks. Matt edited to add: I have seen lots of folks lose chicks to the mess that ducks make. The ducks get everything wet and that includes chicks which die easily from a chill. I would keep them seperate.