I agree with JLC.

I currently have a 20 gallon long with a sliding screen top. I have a lamp (with a 50 watt Red bulb in it) and an UTH. I have the UTH on 24/7 with a waterdish on top of that to help generate some humidity. I only turn my lamp on right after he eats to give him a little more heat. I also mist at least 2 a day, and my humidity runs around 50 - 55% with out the lamp on. But with the lamp on it goes down, but I mist more often when the lamp is running.