Eheim Jager Thermostat Aquarium Heater Unboxed & Tested (Review 2024)

At first glance, the Eheim Jager Thermostat is huge. And it is. It’s massive.

But how does it perform? And how does that performance stand up to other heaters?

To find out, I purchased the 200W Eheim Jager Thermostat and tested it on my tank to get you real world data on how this heater performance every day.

In this review, I’ll go over how I tested it, what I liked and didn’t, how it compares to others, and my overall thoughts on this aquarium heater.

Eheim Jager Heater Review Overview

Eheim Jager Thermostat aquarium heater review scores bar graph

This is a quality heater that will definitely get the job done. It heats efficiently and will provide a consistent temperature.

I do find it to be a bit oversized, but the large surface area does make it easier for this heater to keep the water at the right temperature.

Although it is a solid performer, it is missing some of the features I look for in a heater, like a heater guard and an overheat sensor.

It does have an indicator light for active heating mode, but doesn’t have a standby mode light.

But, overall, this Eheim is well worth the money and definitely goes on my short list of possibilities when considering new tank equipment.

Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black
Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black

    Last update on 2024-07-14 / Commissions Earned / Images from Amazon Product Advertising API

    How I Tested The Eheim Jager Heater

    eheim jager aquarium heater submersed in aquarium

    I tested this heater along with four others in a head-to-head comparison so that I could compare and contrast each one against its competitors.

    All five heaters were 200 watts so I could do my best to compare apples to apples.

    I set up each heater individually in the 55 gallon (208 liter) cichlid tank in my living room. I let each heater run for a week and took notes on things like how easy they were to install, calibrate and how consistent the temperature was.

    I installed five different thermometers along the front glass of the tank so that I could easily note the temperature several times a day and make sure that the heater was able to keep up with heating the entire tank.

    If you’re looking for a reliable thermometer, please check out this article where I put several different thermometer brands to the test.

    This tank is kept in a climate controlled room with an average temperature of 70°F (21°C) and the goal was for the tank water to stay at 75°F (24°C).

    I tweaked and adjusted the heaters as much as was necessary to get them to hold the water 75°F.

    Features I’m Looking for in a Heater

    There are a lot of different heaters out there on the market. They come in all sorts of sizes and shapes and with a variety of optional features. Here are the features that I look for in an aquarium heater:

    • Easy to read temperature settings – some heaters have horrible temperature control settings. On some, you can’t see what temperature you’re setting the heater for. I even had one that didn’t tell you what direction on the dial increased the heat and which way decreased it. I greatly prefer heaters that have easy to read settings.
    • Durability – the outside of a heater may be glass, ceramic, plastic, or titanium. I’ve had many glass heaters crack over the years, so I prefer one made out of tougher materials.
    • Indicator lights – indicator lights let you know what your heater is doing. Some have lights that only turn on while the heating element is active. Others have one color light to let you know they’re plugged in and on standby and another color that tells you it is actively heating. Or, worst of all, some heaters have no indicator light at all. I prefer heaters to have at least one indicator light.
    • Overheat/dry sensor – overheat sensors shut the heater down if it reaches a high temperature. Dry sensors shut the heater down if they detect that the heater is out of the water and still running. This is an important safety feature since aquarium heaters can get very hot when they run outside the water. Hot enough to crack the heater, cause severe burns, melt the heater or even cause a fire.
    • Heater guard – a heater guard is a slotted, plastic sleeve that fits over the exterior of the heater and prevents fish from touching the super hot heating tube. I recently lost a school of fish that kept trying to swim behind the heater and burned themselves. So, a heater guard is a very desirable feature, in my opinion.

    Ehiem Jager Thermostat Aquarium Heater Review

    After lots of testing, here’s my review for the Eheim Jager Thermostat Aquarium Heater.

    Eheim Jager 200W aquarium heater unboxed

    This heater is super simple. The box contains the heater itself, which is basically just a big glass cylinder with a temperature dial on top. It has a really nice heavy duty cord, and there are some loose suction cups in the box that you fit into the bracket that holds the heater to the glass.

    So, here’s how the features on the Eheim Jager Aquarium Thermostat Heater measure up:

    Easy to read temperature settings – there’s a nice, easy to read temperature dial on top.

    Aquarium heater controls readability review scores

    Durability – this heater is made of glass and does not have a heater guard. This does mean it’s more vulnerable to cracks and shatters than titanium or plastic heaters. Be extra cautious when draining your tank since quick temperature changes can cause glass heaters to crack or shatter, making the heater unsafe to use.

    Aquarium heater durability review scores

    Indicator light – there is an indicator light that lets you know the heater is actively warming the water, but there’s no light for standby mode.

    Aquarium heaters indicator light review scores

    Overheat/dry sensor – dry sensor, but no overheat sensor.

    Aquarium heater overheat/dry sensor review scores

    Heater guard – no heater guard and the heating tube is much too large for aftermarket heater guards.

    Aquarium heaters heater guard review scores
    Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black
    Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black

      Last update on 2024-07-14 / Commissions Earned / Images from Amazon Product Advertising API

      Eheim Jager Thermostat Pros & Cons

      OK so my first impression when I took this out of the box was that this thing is enormous!

      For this series of heater reviews, I unboxed and tested five different heaters, and this one was by far the largest!

      Even though it doesn’t come with a heater guard, it’s still longer than any of the other brands that I tried.

      This heater is over 16 inches (41 centimeters) long. In contrast, the next biggest, the Fluval E200, is only 13 inches (33 centimeters) long and that’s with a hefty plastic heater guard surrounding the heating tube.

      I know 3 inches doesn’t seem like a huge deal, but a 55 gallon is only 21 inches (53 centimeters) high and that’s the outside glass, the inside is more like 20 inches (51 centimeters). So, when you add in substrate, getting a 16 inch long heater to fit along the back wall can be dicey.

      And the tube isn’t just long, it’s also two to three times bigger around than similar heaters. Luckily, I could just get it to fit without it touching the substrate or hardscape. 

      This leads me into some of the things that I don’t really like about this heater.

      The heating tube is made of glass, so it’s vulnerable to cracking and shattering. 

      It doesn’t come with a heater guard. Any fish that touches that heater while the element is on could get burned. And the exterior is so huge there aren’t really any aftermarket heater guards that will fit over it.

      I will say though, that this is a very efficient heater that does a good job of holding the tank at a steady temperature. 

      Calibrating this heater can be tricky. The dial that you use to set the temperature works a bit differently than other heaters.

      It’s kind of confusing, but I’ll give explaining it my best shot. 

      For most heaters, you set the dial to the temperature that you want, but the heater may not actually heat the water to that temperature. 

      You might set it for 75°F, but the actual temp ends up being 78°F. Then you just have to mentally figure in that the actual temp will be however many degrees off from what the dial says, and you just have to live with it.

      This can make adjusting the temperature confusing and difficult.

      With this Eheim you can actually calibrate the heater to your individual tank so the dial matches the true temperature of the water.

      Then you don’t have to do mental gymnastics and quantum calculations every time you need to reset the temp on the heater.

      I like this feature, even if it’s a little hard to understand at first. It means that you can truly dial into the right temp, instead of just having to live with the factory calibration that may not be accurate in your particular tank.

      And Eheim is one of the only manufacturers that lets you calibrate a heater like this yourself.

      There are two rings on the top of the heater: a blue ring that has the numbers printed on it and a red ring that has an indicator arrow that sticks out.

      When you’re first setting up the heater, you turn the blue dial until the red arrow points to the temperature you want. Then let the heater run for a day and keep an eye on the temp.

      If the temperature is off, you move the red ring so that it points at what the actual temperature is. So, if you set the heater for 75°F, but it’s at 78°F, you would turn the red arrow until it rested on 78°F.

      The heater would then be calibrated to your tank and you can turn the blue dial and set it at the temperature you want.

      I did have to fiddle with this heater to get it calibrated to my tank. It took me about five times to finally get it to hold the water at 75°F.

      But, once I got it calibrated, it did a great job holding the temp steady. I was impressed by the consistency.


      • Efficient and consistent heating
      • Dry sensor
      • Easy to read settings
      • Precise calibration


      • Large footprint can be tough to fit
      • Exterior made of glass
      • No heater guard and too big for aftermarket heater guards
      Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black
      Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black

        Last update on 2024-07-14 / Commissions Earned / Images from Amazon Product Advertising API

        How Does The Eheim Jager Compare to Other Heaters?

        Aquarium heater review results bar graph

        I do have to say that this heater was bested by the Fluval E200, the Hygger 200W Digital Quartz Heater and the Fluval M200

        It seems almost unfair to compare anything to that Fluval E Heater since it has so many advanced and just plain nifty features. It even bests other Fluval heaters, it’s amazing!

        But, if you’re looking for a simple workhorse of a heater, this Eheim is a great choice. 

        It definitely outperformed the HITOP heater I tested as far as consistency and calibration. It was also much easier to install than the HITOP.

        You can read the full round up review for the best aquarium heaters here.

        Final Thoughts On The Eheim Jager Heater

        This monster heater certainly makes an impression. 

        I would say that this heater is best for tanks that are 55-60 gallons. It’s a better fit for tall tanks since the heating tube is so long.

        While this wasn’t my top pick from the head-to-head challenge, I do think that this is a solid and economical heater that does a great job of holding the water at a steady temp. 

        The bigger heating tube means there’s a large surface area that contacts the water, making heating more efficient.

        It’s a simple, old school heater that will get the job done.

        I hope you find this article helpful.

        I wish you and your fish the very best!

        Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black
        Eheim 3619090 Jager Aquarium Thermostat Heater 300W, Black

          Last update on 2024-07-14 / Commissions Earned / Images from Amazon Product Advertising API

          Katherine Morgan
          Katherine Morgan

          Hey, there! I'm Katherine from Northwest Florida. An aquarium specialist, I've kept tanks for over two decades, enjoy experimenting with low-tech planted setups and an avid South American cichlid enthusiast.

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