ReptiTherm Under Tank Heaters are an ideal 24-hour primary or secondary heat source for tropical or temperate reptilian species. All of Zoo Med's Under Tank Heaters are UL/cUL approved (GS/TuV/CE in Europe) and contains a solid state nichrome heating element. These under tank heaters permanently adhere to your terrarium, forming a solid bond for optimum heat transfer. Inexpensive, low wattage heaters. Excellent secondary heat source. Q: Where do I put the Under Tank Heater? A: The Under Tank Heater can be placed underneath the tank or on the side of the tank depending on your set up. The Under Tank Heater should be placed on the outside of the tank only. If you choose to place the heater on the underside of the tank, be sure to elevate the tank slightly using the included “bump-on feet” or another method to prevent heat encapsulation. Please be sure to read the instructions carefully. Q: How much will the Under Tank Heater heat my tank? A: Depending on the mounting, substrate, and other conditions the UTH can bring the temperature up by 2-8 degrees. Q: Can I use the rheostat/thermostat with Reptitherm Under Tank Heater? A: Yes! We recommend using a rheostat or thermostat if your home reaches 80 degrees or warmer. Q: Can I use this heater on my aquatic tank? A: No. This combination can create stress cracks. Q: Can I use Aspen Snake Bedding or shavings with the Under Tank Heater? A: Yes you can but if using very lightweight substrates such as pine shavings or sphagnum moss, you must put a layer of Zoo Med's Eco Carpet down first. This prevents snakes and burrowing reptiles from pushing substrate aside and resting on top of the glass directly above the heater, resulting in possible burns.