well ever since i bought my uth, ive used teh astro turf bedding. warm side was at 87 degrees with humidity of 42. still got a perfect shed with that. well today i switched to aspen substrate and now the temp is at 89 with a humidity of 70 percent. ( i know thats too high, but i just cleaned out the tank this morning to so its a bit damp in there). Ill keep yous posted if your interested