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Hydor Theo Heater

Internal aquarium heater for all aquariums

At a glance...
  • A robust, efficient aquarium heater for all tanks
  • Features a secure, suction cup fitting
  • A range of sizes to suit all tanks
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Fantastic aquarium heaters that are a breeze to set up. If you’re setting up a tropical aquarium, these are a great choice.

What are Hydor Theo Heaters?

Hydor Theo Heaters are a range of durable and reliable fish tank heaters. With a simple design, featuring a shatterproof glass tube and mounting clips, each Hydor heater is easy to set up and maintain. The heaters have been designed to be as energy efficient and minimalist as possible, allowing them to blend into the background of your tropical aquarium to give the beauty and colours of your fish centre stage.

What are the features of these aquarium heaters?

The heaters are packed with safe, intelligent features that not only ensure your fish are in the right water temperature, but that they are safe as well. The entire unit can be positioned horizontally or vertically and is fully submersible so you can place it wherever you need to heat your aquarium. The patented PTC heating system reduces power on a graduated scale in the event of abnormal functioning, as an anti-thermal shock feature to protect your fish and aquarium.

What's the difference between products in this range?

This range of heaters comes in 6 different sizes, increasing in both Wattage and length as you go up the range. Generally, the bigger your tank the bigger the heater you will require and the more power it will use. Check below to find the exact heater you will require to keep your tank tropical.



Brand Hydor
Guarantee 2 year


Model Dimensions Wattage Recommended tank volume
Hydor Aquarium Theo Heater 25w 30x178mm 25W 10-20l
Hydor Aquarium Theo Heater 50w 30x178mm 50W 20-50l
Hydor Aquarium Theo Heater 100w 30x226mm 100W 50-100l
Hydor Aquarium Theo Heater 150w 30x306mm 150W 90-150l
Hydor Aquarium Theo Heater 200w 30x306mm 200W 100-200l
Hydor Aquarium Theo Heater 300w 30x394mm 300W 200-300l
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