A Breakthrough in submersible heater technology now available from All-Glass Aquarium. All-Glass Aquarium introduces the latest in aquarium heater technology! These new UL listed heaters feature state-of-the-art technology, employing a patented heating film and special shatter-resistant glass to provide extra durability and even heating. Heaters can also be submersed in either vertical or horizontal positions, making it easy to conceal them in aquariums. Heaters will also automatically shut off when they are not properly submersed.