Quote Originally Posted by ckuhn003 View Post
From the sounds of it, you're not taking the surface temperatures of your tank which is what you need to be concerned with. You can achieve this by using a temp gun. I say this because I don't think your house temperatures are going to influence huge 10 degree swings in surface temps; especially if you have a working thermostat controlling your heat mats. It sounds like you may be using a regular thermometer to take air temps inside your tank. Does this make sense?
I actually have a thermometer on either side and the probes are against the surface of the tank, covered by the substrate. What you say makes sense though.