I have a zoomed 8" x 12" heat mat in my 18"long x 18"wide exoterra that covers just under 1/3 of the tank. It has 1 inch of hydro balls at the bottom of the tank. Then on the 1/3 side of the tank I have a medium size zoomed Repti Shelter
Repti Shelter? 3 in 1 Cave as the humid hide, placed directly on top of the mesh separating the hydroballs from the soil (over the heat mat). Then I also have a cork hollow half buried at approximately a 30 degree angle going down till it touches that mesh as well for a dry hotspot (again over the heat mat)
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. Both spots get around 85 degrees Fahrenheit, while the heat mat it self, when I measure it with a digital temp gun, registers at 90 degrees Fahrenheit. The coldest spot in the tank is 68 degree. I have my heat mat on a lamp dimmer set to half the normal voltage, so it runs at 8 watts per hour instead of 16 watts(which was heating up to 135 degrees) . I pay 13 cents per 1000 watts, so at 8 watts per hour (70,080 watts per year multiplied by 13 cents per 1000 watts) it only cost me $9.11 per year to run it. If I didn't have the hydroballs in the way I would be able to further dim down the heat mat by 5 degrees, saving around .50 cents a year, but loosing all the humidity I get from it (around 60-70% with the heat mat under the hydro balls, as apposed to 30% with the heat mat up above the substrate). For geckos that don't have eye lids, I imagine that trying to sleep without having your eye balls dry out must be awfully irritating. My house stays at less than 30% humidity all fall-winter so, this added humidity in my tanks are welcomed, and I am sure my geckos appreciate it.
In this picture the gecko is a female Paroedura Pictus (which are not known for requiring high humidity) and the red light above is just an L.E.D. for night viewing and doesn't add any heat.
