I am very new to having chickens, and have my first batch of 16, 3 day old chicks in a large Rubbermaid tub in the bathroom. Originally I had planned for them to be raised in the coop, but the overnight temps here are fluctuating all over the place from the high 50's to the low 70's...I have sand on the coop floor and have heard that sand is not good for babies...what is the earliest age that chicks can tolerate sand, and at what age range can I let them free inside the coop? As my moniker implies, I have a lot of experience with dogs, but none with poultry! TIA...