THEO Heater - 25W - Up to 7 gal.

4 Reviews
SKU: 205248
Manufacturer: Hydor
MPN: T11702

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Provide your tank with the proper temperature with the most advanced heating technology available. THEO heaters are designed with a peculiar cylindrical shape that renders them virtually shatterproof. Fully submersible, THEO heaters function with the PTC (Positive Thermal Coefficient) heating element, a special polymer sheet silk-screened with heating ink (like your car's windshield defroster), that enables them to run dry for a short time without damage. With an easy-to-read temperature dial, these heaters are the simplest, yet safest available.

25w model is rated for 2-7 gallon aquariums.

For complete product information, download the instruction manual.


Length7 in.
Width0.75 IN. DIAMETER
Max Wattage25
Warranty2 year
UL ListedYes
Internal Id


For complete product information, download the instruction manual.

Ratings & Reviews

4 reviews

  • 4 stars
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  • 2 stars
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Really powerful little heater


I bought this heater to use in my Fluval Spec V nano reef tank. This thing is GREAT! Heats up the water quickly, and its slim profile fits in the pump chamber with room to spare, although I had to nix the suction cups (no big deal, though). I highly recommend.

Works quite well


Very pleased, does a great job in my Fluval Edge 6 gallon.

Great heater for small tank


Excellent consistency.

Hydor Theo 25W defective


When I first put this heater in my tank, it went on and off randomly although it wasn't near the temperature at which was set. I returned it.
<br>The heater is very small, but I'm not sure that's a good quality. The smaller the heater element, the smaller the surrounding area of water that gets heated.