Im very new at this and dont even have my snake yet. But have been researching to no end to get my home built right for my new addition soon. Im certain that the UTH or Heating pad should be on the exterior of your tank not inside. Seems only bad things can happen like if the snake moves the substrate and comes in direct contact with it, if water gets spilled on it , it could electrocute or cause a fire. I also read that the UTH should only cover about 1/3 of one side of the tank as to allow for gradual temperature decline from warm side to cool side.