I use a 50-50 clean top soil and play sand moistened enough for the dragons to dig into without it collapsing. I put the dirt into a large Rubbermaid and angle the dirt on one side like a slope with a dome light clamped on the side shinning on the slope. Here are a few sites with good info on egg laying and incubation. WWW.Dachiu.com and copy and paste the following too for more info.
http://www.biology.lsa.umich.edu/research/labs/ktosney/file/BDcare.html
Here is a pic of my female Amber laying her infertile eggs. Amber does not breed for me so she lays infertile clutches. Just wanted to show how I set things up and how she was able to dig into the mound.

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