If the heating pad does not provide enough heat.

[Dog Shrink]

What about a ceramic heat emitter? Those are designed to raise the ambient temps of your tank rather than a heat bulb which is more to raise the temps in a certain spot in your tank. Things don't always dry out as fast using a heat emitter rather than a heat lamp.

[Sierra]

Also, I think it depends on where the thermometer is in the tank, so if your thermometer is on what would be the colder side of the tank, that might affect it too

[jaguilar15]

I might have to try the heat emitter, but as others said, as long as the substrate stays at a warm temperature it should be fine. and It makes sense to me =]