A thermostat is NOT optional for your Uth. You can find fairly cheap ones on amazon. They're called Hydrofarms. Your UTH can easily reach over 110• f in less than two hours. If you have the money, invest in a herpstat.
http://www.spyderobotics.com
Is your thermometer analog or digital? Does it come with a probe? If its one of those circular thermometers, chances are your temps are much different than what you think they are.