I seem to have the same problem with my new ball python's enclosure. I have a probe under the substrate right above my uth and also two thermostats measuring the cold and hot sides. I also have a 100w basking light used in a ceramic heating lamp fixture. The substrate I am currently using is Eco earth loose coconut fiber substrate blend. The tank is 20 gallons long and has a mesh metal top. The light fixture is positioned on the hot side right above the hiding log I have in the enclosure. The temperature on both the thermostat above the uth and the hot side never exceeds 85 degrees but is normally at 80-82 degrees, the cool side reads only 70 degrees, and only sometimes gets up to 73-75. I do not have a red or black bulb yet ( I Plan to buy one today) so I had to leave the light and pad on last night. I was wondering if maybe I should get another fixture and place a red or black bulb towards the cool side to try and get the cool side up to a steady 75 degrees and the hot side to 85 degrees. I would be changing the 100w day bulb to a ceramic heating bulb that produces the same heat with no light emission for night. Does this sound like a good idea? I am very new to this so any help would be not only greatly appreciated but also will benefit the quality of habitat for the snake. Thank you.