THEO UL Aquarium Heaters from Hydor 50 Watt

The health of your fish depends on reliable, consistent temperature control. These shatterproof submersible heaters maintain temperature with a precise micro-switch, and meet exacting UL standards for safety. They utilize a patented technology of conductive particles and thermo-sensitive organic resins to allow heat resistance to increase along with temperature--assuring that the unit cannot overheat even when out of water. The heaters can be utilized either vertically or horizontally, and are fully and safely submersible.