Hydor THEO Submersible Aquarium Heaters

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 25W/50W & 100W/150W models, at 7" & 8.9" respectively, are among the smallest sized heaters on the market. The Theo ‘minimum water line’ requirement must be followed for proper operation.

Manufacturer Warranty: 2-year from date of purchase
Hydor THEO Submersible Aquarium Heaters
Reef Aquarium
Item #DescriptionLengthCapacity with 8°FCapacity with 22°FPrice 
HD11302Hydor THEO Heater 200 Watt12"26-53gal48gal$27.99
HD11402Hydor THEO Heater 300 Watt15.5"53-80gal74gal$30.99
HD11502Hydor THEO Heater 400 Watt15.5"80-105gal85gal$34.99