Theo 50W for aquariums 5â€“14 gallonsNew aquarium heater functioning with the exclusive PTC (Positive Thermal Coefficient) technology.The Hydor Theo heater line features PTC patented thermal technology which makes it among the safest aquarium heater lines on the market. UL Listed by design, not by the use of accessories. Made from specially engineered shatterproof glass which, while not unbreakable, is designed to resist breakage in most normal aquarium situations. Highly accurate due to the use of precise micro-switch technology. For use in freshwater and marine aquariums. The 50W & 100W/150W models, at 7" & 8.9" respectively, are among the smallest sized heaters on the market. The Theo â€˜minimum water line` requirement must be followed for proper operation.Features:The first shatter-proof heater thanks to the peculiar glass tube.Maximum security: THEO is shock resistant thanks to the PTC heating element and the shatterproof glass tube.Free positioning in aquarium with supplied suction cups.Self-limiting: the patented PTC heating system guarantees operation in complete safety because in case of dry running there is no danger for damage.Two year manufacturer`s warranty.