Approximately 1/3 of my substrate is heated with heating cable from underneath the cypress mulch and spagnum moss substrate. The heated portion is underneath the "brush pile" so pockets of warm air exist that they breathe during the night while they are sleeping.
I just barely came across heating cables for the first time in Farm tek magazine. I was eager to find out if there were ways it could be used for tortoises. VERY COOL!
I learned it on here a long time ago... I can try to find the habitat plans where it talks about under-substrate heating cable like this. You bend about an inch or two on each side of a piece of wire hardware cloth with 1/2" x 1/2" squares, then cable tie your heating cable to the bottom of the wire mesh, THEN cover it in substrate. That way the torties cannot lay right on the cable, even if they burrow.
