Hi there, I have two one week-old chicks, and I'm wanting to start taking them outside and maybe give them a few treats. I know they have to have grit, and I have some play sand that I boiled (so it is sterilized) and I just want to know if that is okay to give them. I've also heard of using finch grit from the pet store. I'm curious, what is everyone's opinion on this? Thank you!