Hydor Theo Aquarium Heater 100w Made in Italy The Hydor Theo heater is an essential aquarium component for maintaining accurate and safe water temperatures in any tank. Theo is a secure, functional and aesthetically appealing product. Main features: Shock-resistant thanks to the shatter-proof glass used to make the product. Resistant to thermal shock Totally submersible Operates vertically and horizontally Controls its own set temperature* For aquariums 50-100 litres Length 22.6cm Australian Plug The inside of the glass tube is made with PTC film, enabling the device to control its own temperature and to limit power in the event of irregular function thanks to carbon aggregates that, by moving away from one another, increase resistance.