Have used Kiln dried sand for years now in the young bird loft and found it to be very good.
I think it helps eradicates a good few ailments in young birds as they tend to build up an immunity to various diseases, as they are always picking about in it.I find I treat less for things. Buy a riddle from the garden center and riddle once a week.The sand can last for the whole young bird season.This my own opinion and I have not had young bird sickness in years. My bird are always in good condition.
Dougie