There are two reasons I add sand at week 2... one for them to start getting some grit in the gizzard to help it develop so I can start giving treats, and the other is to see how long it takes them to start dust bathing (just for fun).. 30 minutes and one was busy taking her first bath. Forgot to mention, it also helps build their immune systems by using 'native' sand and not the store bought variety.Cute.
Another good thing to do with sand?
.....is fill 8 or 16 ounce sour cream containers to put your feed and water on top of.
Keeps them much cleaner.