i have a year and a hlaf old ball. i live in colorado and its dry here and im having trouble keeping up the humidity in his cage. i have and under tank heater but im not using it because im afriad it wont heat the tank enough. i use a daylamp and a night lamp. the humidity will drop to 15-20% during the day. i have even covered half the cage with drop plastic you would use for painting as a moisture barrier. i use fur bark as a substrate. i have a pretty good size water dish in there as well. what would anybody suggest?