If you have a tank with a screen lid, I suggest you should cover a little more than half of it with a warm damp towel or a plastic sheet. You could also duct tape the lid. If you use a UTH, duct tape the entire lid and cut out a square maybe 5-6 sq. inches so the snake can breathe. I'm sure this will keep in the humidity when you mist. You also switch over to tubs if you do not use them. They are pretty light weight and great for holding in humidity. Though, you also can switch over to Cypress Mulch (as stated before) because it retains in humidity very well. Also, Coconut Husk and Bark Chips retain in humidity very well too.