I use heat lamps in conjunction with a UTH... I have a 40g glass breeder with a screen top. 100w IR during the day, 75w blk at ngiht. Keeps my bottom temp at 85, basking temp around 92. Yes, you will get a humidity drop. I use a Tropic Aire humidifier / exchanger with a Rena pump pushing it, and it works great. Keeps my humidity in the 55-58 range.