I have a baby ball in a 10 gal tank. I am using an UTH (with about 1" of dirt on top) as well as a UV light, and the temperature usually hovers between 87 -91 degrees. The one night I turned off the UV basking light, the temperature dropped to about 73 degrees, so I apparently need to keep the UV light on as long as it is in that room. I don't have a temperature control on the UTH, so do I need to put a separate thermometer on the UTH itself, like at the dirt level?