Last update: December 7, 2023

Reviewing the Eheim Jager TruTemp Aquarium Heater

If you have been in the hobby for a while, then you have no doubt heard of the Eheim Jager TruTemp, a German-made aquarium heater that is highly regarded for its accuracy and quality.

Today, I am going to put these claims to the test, including answering the very important question…

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05/27/2024 08:29 pm GMT

Is this heater worth your money?

So, join me as I share my experience with the Eheim Jager TruTemp.

With that out of the way, it’s time to jump into my review!


Different sized Eheim Jager TruTemp aquarium heaters compared side by side

Don’t have much room to spare? Use the following table to determine if the Eheim Jager TruTemp heater will fit inside your aquarium.

SizeTank (up to)LengthWidthHeight
50w16 gal9.55″1.4″1.65″
75w26 gal10.6″1.4″1.65″
100w40 gal12.55″1.4″1.65″
125w53 gal12.55″1.4″1.65″
150w79 gal13.58″1.4″1.65″
200w106 gal15.98″1.4″1.65″
250w159 gal17.79″1.4″1.65″
300w264 gal19.92″1.4″1.65″

Note: All measurements of the Eheim Jager TruTemp heater are taken at the longest point when resting in the mounting bracket. The glass heater tube is just 1″ wide.

The following specifications remained constant across all models.

Country of manufactureGermany
Power cord length5.5 foot
Temperature range65 – 93°F
Outer casingGlass

What’s in the box?

Aquarium heater, mounting clip and suction cups included in box

Inside your Eheim Jager TruTemp heater box, you will find…

  • 1 x Eheim Jager TruTemp heater
  • 2 x Suction cups
  • 1 x Mounting bracket

Oh, and an instruction manual. Make sure you read it before setting the heater up in your tank!

You will also find a white plastic ring, like this in the box…

Eheim Jager TruTemp white plastic packaging for protection

This can be discarded, it’s only there to keep the heater safe during shipping and serves no other purpose. So, don’t stress if you open your box to find this plastic ring broken – it’s better that it breaks instead of your heater, right?


Eheim Jager top, bottom and side photos

For a glass aquarium heater, the Eheim Jager TruTemp is actually a looker. The design is modern and, were it not for the bright blue and red temperature dial with readjustment ring, almost formal.

As I held the heater in my hand, I began to appreciate the workmanship. It felt solid, well-made and the plastic is free from burrs and imperfections. When it comes to product build quality, the Germans really know their stuff.

You can clearly see the heater neatly coiled around and around through the special laboratory glass tube.

Nickel chrome heater coil clearly visible through the glass of the Eheim Jager TruTemp

But more than anything else, what really stands out is the size. This heater is long. And, the difference becomes particularly obvious when you compare it side by side with other aquarium heaters…

Eheim Jager TruTemp compared to Hydro Theo, Cobalt Neo-Therm and Aqueon Pro

And that’s just the 50W size. The difference in size becomes even more obvious with the larger models.

At the top of the heater, you find the adjustable thermostat. Simply twist the external temperature controller to select a temperature ranging from 65 – 93°F, marked in couple degrees intervals. That is the largest temperature range of any aquarium heater on the market.

Eheim Jager TruTemp thermostat selector dial

When looking at the power cord, I found myself thinking…

The Germans must really think bigger is better.

Just like the heater and temperature range, the power cord is larger than any other aquarium heater. Check it out…

The thick power cord of the Eheim Jager TruTemp compared to other aquarium heaters

Now, you could look at this like it’s a good thing – the extra-thick insulation on the cable will stop the cord from getting damaged.

However, in over 30 years and dozens of tanks, I have never had an titanium aquarium heater fail because of the cable. In fact, I don’t think I have ever spoken to someone who would benefit from an extra chunky cord.

I found the extra bulk of the cord to be an inconvenience, especially when trying to keep the cord neat and out of view. The chunky cord kept wanting to do its own thing, twisting back into view. Compared to the flat cords of the Hydor Theo and Aqueon Pro, the larger cord feels cumbersome.

Eheim Jager TruTemp aquarium heater holder

Finally, you have the mounting bracket. Simply attach the two suction cups, and you are ready to attach the Eheim Jager TruTemp to the glass of your aquarium.

Eheim Jager TruTemp resting in heater holder

The mounting bracket neatly clips around the glass tube of the heater and can be positioned at any point along the glass section.


Like other aquarium heaters, the Eheim Jager TruTemp kicks into action the moment you plug it into your power strip, so make sure you have it in flexible placement before you turn the power on – this thing gets hot quickly!

While I could easily mount the smaller sizes either vertically or horizontally, you’ll likely want to mount the larger sizes horizontally. Measuring up to 20 inches long, they can take up a fair amount of room in your tank. I also found that mounting the heaters horizontally caused the aquarium to heat up more evenly, although with adequate water movement, this is hardly an issue.

When mounting horizontally, I felt that the larger-sized Eheim Jager heaters needed a second mounting bracket and suction cups. Clipping the mounting bracket to the center of the heater meant that very little pressure on either end would cause it to pop out.

If you do choose to mount the heater vertically, you can leave the thermostat control out of the water for easy access. Just make sure the water covers the ‘minimum water level’ line, and you are fine.

Eheim Jager TruTemp aquarium heater minimum water level indicator

For most people this won’t be essential since once the desired temperature is set, it’s usually never adjusted again. So, if you want to completely submerse your heater then go right ahead.

I will also add that Eheim Jager TruTemp has a run-dry shutoff. If it detects that the heater is getting too hot (out of water) it will turn the unit off – saving your heater from damage. I can confirm that this convenient feature works, and it works well!

Speaking of the temperature control… The dial is stiff to turn. To the point that if you have arthritis or weak fingers, you might actually struggle to twist it. However, this could also be a blessing since it means you are less likely to accidentally change the actual temp if you bump the dial while cleaning.

Given that the Eheim Jager TruTemp is widely regarded for its accuracy, which I discuss later in this review, I find it odd that the temperature selector arrow covers up so much of the markings. It did make it difficult to determine if I had selected the temperature I wanted.

Check it out…

Close-up on markings on Eheim TruTemp thermostat dial

Now, this isn’t the biggest issue since you should always double check your temperature setting with a good aquarium thermometer anyway. But given that Eheim’s focus was on precision, this selector seems like an odd choice. If it was up to me, those temperature marking lines should extend to the edge of the blue dial.

Once you select the correct temperature, it’s time to turn the power on. An orange indicator light located on the front of the glass section lets you know that the adjustable heater is on. Once the water has reached your preset temperature, the unit stops consistent heating, and the LED light changes color to green.

Eheim Jager TruTemp orange LED heating indicator light

It might be simple, but it allowed me to easily check what the heater was doing with a quick glance.

Now, I make it no secret that I typically don’t like glass aquarium heaters. Not only do they often get condensation inside, but they can easily break. Eheim claims that the glass on their heater is both shock-resistant and shatter-proof.

I just had to put it to the test…

So… I performed a drop test, simulating bumping the heater off the counter while cleaning my aquarium – by rolling the heater off my 24-inch-high desk.

Safety mechanism glasses on… I rolled the heater off my desk, squinting in horror at thought of the mess I would soon have to clean up.

The heater landed on my tiled floor with a loud ‘tink.’ And to my surprise, the glass heater tube didn’t shatter. It didn’t even crack…

Scratch on the Eheim Jager TruTemp heater glass tube after being dropped

Besides a small mark, the glass was completely unharmed. I submersed the heater in my aquarium, and it still worked, perfectly. Not bad at all!


Now we get to what is the most important part of the review… Just how accurate is the Eheim Jager TruTemp?

Eheim Jager aquarium heaters are well-regarded by many expert fish keepers for their accuracy, so I was excited to put these claims to the test.

And to do that, I used the following equipment…

Thermal imaging camera, thermometer and probe test equipment for aquarium heater accuracy

I wanted to be confident in my review, so I tested using the following equipment…

  • Flir Thermal Imaging Camera
  • Fluke Digital Thermometer and Thermocouple Probe
  • SP Scienceware Liquid Thermometer

All calibrated with NIST certification.

Eheim Jager claims that their range of heaters are calibrated to an accuracy of ± 0.5°C, which translates to ± 0.9°F.

That is to say that if I adjusted the thermostat to 78°F then the actual water temperature could be 77.1°F, 78.9°F or anywhere in between.

So, I tested the heaters by attempting to warm my aquarium to an even 78°F, measuring the results.

How did these claims compare to real-world testing? Quite well actually. I found that no heater that I tested was out by more than 0.6°F, which falls well within Eheim Jager’s claims of accuracy.

With impressive stats like that, the Eheim Jager gives the accuracy of the Cobalt Neo-Therm a good run for its money – especially if you want to heat your tank to an odd-numbered temperature (the Cobalt Neo-Therm heats in increments of 2°F).

Should you buy it?

If you want a glass aquarium heater, then this Eheim Jager TruTemp is as good as it gets.

It’s massive temperature range beats out any other aquarium heater on the market. If you need your aquarium heated to an unusually cool or warm temperature, then this is really your only choice.

Besides a few quirks with the size and temperature knob, the heater is a great example of German engineering.

A well-made, accurate aquarium heater at a reasonable price. Highly recommended.

I give it 4 / 5 starfish.

Eheim Jager TruTemp thermostat aquarium heater
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05/27/2024 08:29 pm GMT

What do you think of the Eheim Jager TruTemp aquarium heater? Let me know in the comments below!

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

Comments (18)

Thank you for the review! I received my 200 watt Eheim jäger heater today. I hope it works as well as your review about it ????

Hi Akshay,

It’s a great all-round heater than can hold it’s own with the best. I’m sure you will be happy with it.

Nice review.
Unfortunately I purchased this thermocontrol Eheim jager series, and found out it doesn’t have the green LED indicator. Just the orange lamp. The tempcontrol e series is the one with red/green indicators. Too bad it isn’t available in India.

Hi Neo,

I was unaware, thank you for bringing this to my attention. I wish I could address the issue of different models being available in different countries, but I can only test what is available here in the USA 🙁 I hope you are still finding it to be a reliable heater!

Yesterday I bought an Eheim Jager 50W from a national pet store in the US, and it doesn’t have the green light. Just the orange light, like most heaters.

I set it to 77° and was surprised the next morning to see the water at 83° and the heater light on. I understand that they’re meant to be calibrated, but was surprised that they leave the factory that far off. Other than that, I’m impressed by the heater’s build quality, especially the heating element.

We had one in an Aqueon 20 gallon high. If I set it to about 76, it would warm the aquarium to the 80-80.5°F that we wanted for Endler’s Livebearers. So, at least ours did not live up to Ian’s high standards.

Hello. Wanted to find out which of the below heaters you recommend for a 10 gallon tank:

Eheim Jager 50w
Aqueon Pro 50w

I have a ronco thermostat/controller that I’ll be using with it if it matters. I know it’s a bit of overkill for a 10 gallon tank but I already had it laying around the house.

Thanks so much.

Hi Becky,

Currently, Aqueon heaters are highly unreliable – since they moved their manufacturing to china (they used to be made in Italy) I cannot recommend them. I am still testing their newest model, but would hate for you to be the guinea pig if something goes wrong. Of the two, the Eheim Jager would be my recommendation. Also, great score on the ranco temperature controller! I highly recommend them for their reliability, but they are quite expensive. If you have one already, all the better.

Thanks for the reply. I’ll go ahead and purchase the Eheim heater. We have a couple Ranco controllers already from having reptiles. We only have a single, one eyed goldfish in a tank abut keep the downstairs where he is fairly cool in the winter. Didn’t want him to suffer in the cold or be boiled. Wanted to make sure I was purchasing something reliable as he is quite the spoiled fish. 🙂 Thanks again!

Oh I had no idea they were used in keeping reptiles. Although I guess it makes sense given that they require a specialized climate too. Ha, there is nothing wrong with looking after your fish. It doesn’t take long for them to feel like members of the family.

Hello, I have a 3 gallon tank for my Betta & 1 snail. Would the Eheim Jagger 50W be suitable? Is there a 25W? I’d rather err on lightly under than overheat my Betta. I’ve heard horror stories of dead Bettas.


Hi Juliette,

It all depends on the temperature difference outside your tank vs the temperature you want to heat inside your tank. The greater the difference, the larger the heater you will need. You can buy heater controllers that serve as a backup just in case the heater fails.

I have read a substantial amount of overwhelmingly negative reviews on the quality of Eheim heaters on the market today. Amazon, as well as many other online retailers is full of customers with firsthand experiences in which the heater will overheat the aquarium and fail to shut off at the temperature in which the user had set it. This, along with calibration issues, etc., has led many reviewers to come to the conclusion that Eheim Jager heaters, though once the cream of the crop, are no longer the heater that they used to be. Can you shed any light on this concern? I am currently running an AquaTop 300W heater in my 72 gallon bowfront, but it is beginning to make an audible “click” each time it cycles on/off to heat the aquarium. And although it is a 300W heater, it just seems to work very laboriously in order to maintain a constant 78-79 degrees in my house that is kept at 66 degrees. Turning up the heat in the house is not an option. Therefore, I am considering replacing it with the Eheim Jager 300W heater due to many of the positive reviews talking about how much of a “beast of a heater” it is and how the 300W heater seems to perform as if it were an even higher powered heater. I am just concerned with the previously mentioned issues that were experienced by no small number of reviewers. Do you have any suggestions? Thank you so much!

Hi Luke,

There is no foolproof heater. If you can name a heater, there will be a review of it failing. The more popular the heater, the more reviews it will have of it failing – this is largely due to the larger sample size. Given the popularity of the Eheim Jager, and it being globally available, you are going to get more reviews, good and bad.

Even my favorite heater, the Cobalt Neotherm, had a mass failing back in 2012.

In any case, it is best to use 2 or more heaters totaling the total wattage you need in addition to a heater controller. This way, even if a heater does fail, you won’t cook your fish.

I have and index pool 3500 lts and Ibought a heim heater in order to heat it just from 10C to 20 C.
and Iput the heater to 32c for thiw reason.But nothing at all! The water after 7 hours remains in the 10C temperature.Does it needs more time? Or the heater is useless for apool?

Hi George,

Wrong tool for the job, even if you bought the most powerful model, it’s not going to do what you want it to. For a temperature difference of 10C and that much water, you would need a much more powerful heater or multiple heaters. There are heater calculators available online.

I have an Eheim heater, green top and green cord, that I bought in 1995 that is still working great. I did have it stored away for 10 of those years, but I think that is still pretty impressive for an electric heater.

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