Since I live in southern cali I've had humidity issues too - but like K80tik said, check out that sticky about covering the top of your tank. here's the link. Covering the top is pretty much essential with glass tanks, too much heat and humidity escape otherwise. With 3/4 of my screen covered and a little misting every 3-4 days I can keep the humidity at a constant 60%. Once I take off the lid or turn on a fan in the room it goes down to 30% within minutes though so watch out for those things. I'm using desert snow substrate right now but in the past I've used aspen and it worked just fine too. Hope this helps.