The Hydor Theo aquarium heaters are the first shatterproof heaters available on the market due to the sleeve being made out of peculiar glass. This basically means that the glass means that the glass has been treated in such a way in the manufacturing process that it is much stronger. The heater is also shock resistant due to the PTC heating element which uses ceramics and metal combined to produce the heat.
The Hydor Theo aquarium heaters can be completely submerged and stuck to the glass via suction cups in any position. These heaters also come with a rugged cap and easy to adjust thermostat.
THEO 50W - 7 inch - 20/50 l
THEO 100W - 8.9 inch - 50/100 l
THEO150W - 12 inch - 90/150 l
THEO 200W - 12 inch - 100/200 l
THEO 300W - 15.5 inch - 200/300 l
THEO 400W - 15.5 inch - 300/400 l | 
