What's the temperature that the heat pad should be at, if you place it on the bottom of the tank? I don't want to place it in the sides because of aesthetics. I have a back warmer that I'm going to use that I can vary the temperature on. When I place it on the bottom of the tank and I touch the bottom glass, it reads 88 degrees, if I turn it to the next level, it reads 99 degrees. The underground tank heater that zoo med makes reads 106. My frog does dig down to the glass, would the 88 degree heat be safe for him or could I boost it to 99?