Hydor ETH T08104 External Aquarium Heater, 200 W, 12 mm

The Hydor ETH T08104 is a 200 W external aquarium heater for use with external filters or sump tanks. Its electronic temperature setting spans 18° C to 34° C, and the listing recommends it for aquariums of 100 to 200 litres or 100 to 180 litres depending on the stated temperature difference.

At a glance

Designed for external filters and sump collection tanks rather than direct placement in the aquarium.
Electronic temperature control is adjustable from 18° C to 34° C.
The maker describes a PTC heating element intended to protect against overheating.
The listing specifies vertical installation and recommends periodic soft-brush cleaning to limit algae and limescale.

Price

£31.75Save 39%

Reference price: ~~£51.69~~

Price checked: 14 Nov 2026

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Pros and cons

Pros

Keeps the heater outside the aquarium, which can reduce visible equipment in the tank.
Temperature adjustment and stated tank-capacity ranges provide useful selection guidance for compatible setups.
The supplied description includes a fixing eyelet for connecting the heater to aquarium pipework.

Cons

Vertical-only positioning limits installation options.
Requires periodic cleaning of the heating tube to help prevent algae and limescale build-up.

Technical specifications

14 specifications

Heating and compatibility
Power	200 W
Temperature setting	18° C and 34° C
Recommended aquarium capacity	100 to 200 litres with Δ up to 8° C, aquariums from 100 to 180 litres with Δ up to 10° C.
Inner tube diameter	12 mm
Supported setups	Also suitable for external filters and sump collection tanks, it should be positioned only vertically.

Dimensions and installation
Dimensions listed	8 x 7 x 31 cm; 459 g
Weight listed	459 g
Overall heater height	30,5 cm
Mounting detail	Equipped with a special eyelet for fixing, it can be easily connected to pipes or other technical components for aquariums.

Product details
Model	T08104
Colour	Black
Items	1
Use	Indoor
Batteries required	No

What to know before buying

Listing details to confirm

Customer feedback reports some concerns about reliability and longevity, including reports of fish deaths. Treat these reports seriously, but they do not establish a cause or prove a product defect. Monitor aquarium temperature and livestock, and follow the instructions. The listing also gives the overall dimensions as 8 x 7 x 31 cm while specifying a heater height of 30,5 cm. Its capacity guidance varies with the stated temperature difference, so match the relevant Δ condition to your aquarium.

Who is it for?

A good fit for

Aquarium keepers using an external filter or sump who want to keep heater equipment out of the visible tank.
Buyers whose aquarium capacity and required temperature difference fit one of the maker's stated ranges.

Less suited to

Setups that need a heater positioned horizontally or directly inside the aquarium.
Buyers seeking a product with consistently positive reliability feedback.

Hydor ETH T08104 External Aquarium Heater, 200 W, 12 mm · photo 2 — Additional product photo 2

Customer reviews on Amazon

3.6 / 5 · 34 ratings

5 stars43%43%
4 stars15%15%
3 stars20%20%
2 stars7%7%
1 star15%15%

Customer feedback highlights perceived quality, precise temperature retention and the benefit of having equipment outside the tank. Reports about reliability are mixed, while some customers raise longevity and durability concerns, including reports of fish deaths. That criticism matters for a heater used to maintain aquarium temperature, but the feedback does not establish the cause of those outcomes. The overall ratings are mixed rather than uniformly positive.

Positive themes

Customers praise the perceived quality and report that the heater maintains temperature accurately.
Some appreciate the discreet external arrangement and reduced tank clutter.

Negative themes

Some customers express concern about durability and longevity, including reports of fish deaths.

Mixed feedback

Reliability feedback is mixed, with some saying the heater works well and others questioning how long it lasts.

Frequently asked questions

Can this heater be installed horizontally?

No. The listing says it should be positioned only vertically.

What temperature can it be set to?

The electronic control is stated to set temperatures between 18° C and 34° C.

What aquarium size is it recommended for?

The listing gives 100 to 200 litres with Δ up to 8° C, and 100 to 180 litres with Δ up to 10° C. Choose the range that matches the stated temperature difference.

How should the heating tube be maintained?

The product information recommends periodically cleaning it with a soft brush to help prevent algae and limescale.