Hi Sarah and welcome to the forum,

Sand is a no for substrate, I currently have soil and sheet moss. Works well for me, but the cons of having sheet moss is that they get mess up too easily and they are not the cheapest thing that you find on the market ($6 here in California), so you can do some more research in regard to this.

http://www.frogforum.net/tree-frogs/...-question.html

I opened a topic a while back in regards to this matter, I hope you find this useful