I've actually used the thermacare heat wraps. They work for about 8 hours. If you put them on the outside of the glass, they get about as warm at the UTH heat pads. I put a blanket over the tank then. For those of you that have gas heat, the boiling water works well. You can also must with 78-80'F water (dechlorinated, of course, or spring water, distilled water).