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Hydor THEO Heater 300 Watt

Hydor THEO Heater 300 Watt


Item #: HD11402

Temporarily Out of Stock

The THEO heater has all the essential features for maintaining your aquarium`s water temperature precisely and consistently. Featuring patented thermal technology (PTC) which makes it among the safest aquarium heater lines on the market and is 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.

The exclusive technology used and the high quality of the components guarantee a long life.

  • For use in freshwater and marine aquariums
  • Submersible
  • Anti-thermal shock
  • Shock resistance
  • Graduated scale dial
  • Vertical or horizontal positioning
  • Maintains set temperature precisely
Model Wattage Length Aquarium Rating
THEO 200 200 Watts 12" 25-55 Gallons
THEO 300 300 Watts 15.5" 55-80 Gallons
THEO 400 400 Watts 15.5" 80-105 Gallons

Manufacturer information

Hydor has been producing a comprehensive range of equipment for aquariums and ponds since 1984 and offers the best in high-technology for the creation of a living ecosystem at home. The factory has developed thanks to the engineering competence of its founder and its continuous growth is based on the investment it has made in research and the development of innovative technical appliances. A competitive and dynamic structure of more than 150 employees regularly engages in the implementation of products which meet the demands of 50 nations and keep pace with the evolution of the world markets. The global quality is not a simple working method but a daily expression of mind.

3 Stars


Reviewed on
November 09, 2017

No, I would not recommend this.

Good but..

Great heater when it works. I had to turn mine down to 76 to keep the tank at 80. any higher that 76 and it heats the water to 90 degrees!

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Reviewed on
July 03, 2017

No, I would not recommend this.

Fine if you have a controller

Pros: Cheap, small

Cons: don't trust them

Ive had two of the three fail. One in less than a year and the other in a year and a half. If you keep it on a controller they are fine. I wouldn't trust them without a controller. If you don't have a controller just go with a jager or cobalt.

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