Yes, I use THG heat tape in my rack. It costs like $2-3 a foot from pangeareptile.com and I serpentine it back and forth through the shelves so that it is under each tub when finished.

Heres a pic of one of my smaller racks that I built and it's currently housing 5 snakes ranging from 600 to 2200 grams. All tubs are heated by 6" heat tape in the back of the shelves of the rack.

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