Best substrates to use for Chinese Water Dragons?

I have him in a 20g long just temporarily, and he does have stuff to climb on so it's not like he has to stay on the ground. He is a rescue that I adopted and has probably 8 inches of his tail left and not many spines on his back, but he does have some on his cresent. However, he has no missing toes, and probably two missing toe nails. He isn't too big though, so definitely not an adult.

I have to go through the whole humidity problem with glass tanks again. Next week I'm going to try to get a 20g tall enclosure so he has more climbing space. And I will be getting more logs for him to climb on. But I had to tape all of the screen lid besides where the big ass double heat lamp is with his UVB and basking bulb. I mist it a lot when I see it a bit dry, and he is on cypress mulch.

I'm most likely going to put him on sphagnum (sp?) peat moss, it's like 8 bucks for a huge bag at Home Depot and it is a lot easier for me to keep the enclosure humid with that substrate.

Would it be alright if I used the sphagnum peat moss, but if not what are other substrates I can use that would be great to use? I need the enclosure to be like in the 60%-75% humidity range, oh goodie.

At work the moss stays nice and moist all the time, so I'm most likely going to use it. Sorry for the long thread, just had to give you some of the info and my question that needed to be answered.