The UTH does not go in the tank,do not listen to KMG... I put my UTH on the hot side of my tank,I tape ( using aluminum tape) the probe dead center to the pad,not in between the glass and pad but out side of pad that is on the outside of the tank..then I run my thermometer probe inside the tank and tape it to the glass which is under the aspen substrate ,lol, dead center of the heat pad and place my hide accordingly over the pad so center of my hide is center of the pad... Connect it to my hydrofarm thermostat and set for around 89-91 degrees. Works great for me.