Series HT - Submersible Heater/Thermostat Explosion proof aquarium heaters are used for heating water in domestic fish tanks and industrial small water tanks to maintain temperatures between 20-34deg C. The heaters are made from explosion proof glass for added protection and are supplied with suction cups for fitting. A finger adjustable thermostat is fitted for temperature setting. The heaters should always be fitted below the waterline for best use and premature failure. Suction cups to be used on a smooth surface.