hi, yeah that was me who got into a bit of trouble with substrate, i'll say this to you...do not use anything but kitchen roll, its really not worth risking the geckos health, you'll be truely shocked and worried if you see it in your geckos mouth as i did, you feel helpless, as they are so small, and its hard to get it out there mouths. I wanted a natural look, i might have some pics posted on this site of how my tank was at first, it looked nice if i must say so myself

, but after that incident i was not risking it again, my crested gecko pair are 14g and 16g, and an accident happened. Its really not worth the risk, luckily i was there when it happened, so again i advise you to NOT use natural substrate, unless however..you dont feed them live food in the vivarium, feed them live food in a faunarium? or a plastic container of some sought, then they shouldnt have any reason to attack the earth. Note: btw im not telling you what to do, i just dont want you to make a mistake like i did, i'm sure u'd agree with me when i say "geckos health is more important than what it walks on" in the crested geckos case anyways, but hey its your call, goodluck with what ever you choose :D