No offense but I would not use aspen shavings. Ok for snakes, but seeing as you want to maintain moisture and not cause any harm to your geckos (aspen can have sharp edges) I would avoid it. I use paper towel at home here, but I work at a science center with herps and we use New Zealand Sphagnum moss as a substrate. It carries less parasites and lasts longer without getting a rotten smell as other mosses quickly do. It might be a little tough to find at a pet store but you can order it online compacted and dried. Here is a link to something similar. http://www.gardeningwarehousedirect.com/cat_sphagnum.cfm
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12.5.15 Crested Geckos
0.1 Leopard Gecko
0.0.1 Tomato Frog
1.1 Ball Python
0.0.2 Poison Dart frog
www.geckoharmony.com