Aquarium Decoration

Eheim Jager | Aquarium Heater Review

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

Main features of the Eheim Jager

We are going to see first the main characteristics of this high-precision adjustable thermo-heater from the valued Eheim house.

Eheim heaters from the Jager series have the following characteristics:

  • They can be used in fresh water or marine (salt water)
  • Fully submersible design
  • Adjustable temperature, from 18°C ​​to 34°C
  • Temperature accuracy up to 0.5°C
  • TruTemp dial allows heater to be recalibrated
  • Safety system that protects against dry running
  • Comes with a suction cup mount (detachable)
  • It has a lamp that indicates when it is heating
  • Made of shock and shatter resistant glass

Let us now see the technical specifications of this range of water heaters.


The following specifications are common to all models:

  • Country of manufacture Germany
  • The length of the power cable is 1.6 meters
  • The temperature range is 18 – 33°C
  • Outer cover Glass

We now see the specifications of each model:

What does the Eheim Jager aquarium heater box come with?

Inside the box of the Eheim Jager aquarium heater, you will find:

  • 1 Eheim Jager heater
  • 2 suction cups
  • 1 mounting bracket
  • 1 an instruction manual

Be sure to read the manual before putting the heater in your tank!

You’ll also find a white plastic ring, but it’s only there to keep the heater secure during transport and serves no other purpose. So, don’t rush when you open the box and find this ring without knowing what it’s for.

Heater Installation

There is not much to say about aquarium heaters, they are simple devices and should be easy to install. And this heater lives up to that expectation.

It has an adjustment dial to set the temperature. It is the blue dial, and you just have to turn it so that the arrow of the red ring marks the temperature at which you want to keep the aquarium.

The Eheim Jager aquarium heater can be calibrated when it is not making a correct reading. This is done by rotating the red ring.

To calibrate the heater you need an accurate thermometer. If you have the Eheim Jager heater set at 24°C and the thermometer indicates an aquarium temperature of 26°C, you will need to calibrate the heater by rotating the red indicator from 24 to 26°C without moving the blue ring.

Knowing this, the following must be taken into account:

When this heater is purchased, it is assumed to be factory calibrated. There is really no guarantee on this. It may not have been calibrated by the factory, or you may have purchased a returned heater with the ring rotated earlier.

All this is to say that the best thing to do when installing for the first time is to make sure the heater is properly calibrated.

We have seen some reviews of this heater where it did not work as the user intended. It is possible that the heater had a bad calibration, or even the aquarist turned the red calibration ring before he knew what he was doing, thereby unknowingly ruining the accuracy of the heater.

Eheim Jager Design

For a glass aquarium heater, the Eheim Jager has a modern design with a blue and red temperature dial.

The heater feels sturdy, well made, and the plastic is free of burrs and blemishes. When it comes to the build quality of a product, the Germans really know their stuff.

In the heater you can clearly see the nickel-chrome coil wound inside the glass tube.

But what really stands out is the size. This heater is long. And, the difference becomes particularly obvious when you compare it to other aquarium heaters. The size difference becomes even more obvious with the larger models.

At the top of the heater is the adjustable thermostat. Simply turn the dial to select a temperature of 18 – 33°C, marked in two degree intervals. It is one of the largest temperature ranges that we can find in aquarium heaters.

If we look at the power cable of the Eheim Jager heater we will also see that it is larger than any other aquarium heater. The extra-thick cable insulation will prevent the cable from being damaged.

But it must also be said that the extra thickness of the cable can be a drawback, especially when it comes to keeping the cable tidy and out of sight.

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

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


Like other aquarium heaters, the Eheim Jager starts working the moment you plug it in, so make sure you have it in position before turning it on, these devices heat up quickly!

Although you can easily mount the smaller sizes vertically or horizontally, you will most likely mount the larger sizes horizontally. Measuring up to 50cm long, they can take up quite a bit of space in the tank.

It is also true that mounting the heater horizontally heats the aquarium more evenly, although with adequate water movement, this is not a problem.

By contrast, the larger Eheim Jager heaters required a second mounting bracket and suction cups. By attaching the mounting bracket to the center of the heater, the little pressure on each end makes it feel like it might come off.

If you decide 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.

For most aquarists this is not essential as once the desired temperature is set, it is not normally readjusted. So if you want to completely submerge your heater, no problem.

The Eheim Jager has a safety shutdown system. If it detects that the heater is getting too hot (without water) it will turn off the unit, saving the heater from damage.

The dial is stiff to turn, and this means you’re less likely to accidentally change the temperature if you bump the dial while cleaning.

Once the correct temperature is selected, it is time to turn on the heater. To know that the heater is on, an orange indicator light located on the front of the glass section allows you to. Once the water has reached the preset temperature, the unit stops heating and the LED light turns green.

It may be simple, but it allows you to check at a quick glance whether the heater is working or not.

Although many aquarists dislike glass heaters because they can break easily, Eheim claims that the glass in their Jager heater is impact and shatter resistant.


Now we come to one of the most important parts of the review… How accurate is the Eheim Jager?

Eheim Jager aquarium heaters are highly regarded by many aquarists for their precision. Eheim Jager claim that their range of heaters are calibrated to an accuracy of ± 0.5°C.

Although the Eheim Jager is widely praised for its accuracy, it has to be said that some users have complained about the temperature selection arrow covering up the markings so much. This can make it more difficult to determine if the desired temperature has been selected.

Now this is not the biggest problem since you should always check the temperature with a good aquarium thermometer anyway.


Eheim Jager’s line of aquarium heaters are robustly built, accurate, have been reliable in use and are very reasonably priced.

Still, you will notice that this heater is priced slightly higher than some competitors. This range of aquarium heaters has a price that moves around €20-30.

Other aquarium heaters

Conclusions about the Eheim Jager aquarium heater

If you want a glass heater for aquariums, then this Eheim Jager is the best there is.

Eheim Jager heaters are very durable. If you need a large capacity heater for a large aquarium, we recommend that you take this heater into consideration.

Its huge temperature range surpasses any other aquarium heater on the market. If you need to heat your aquarium to an unusually hot or cold temperature, then this is really your only option.

Aside from some quirks in size and temperature control, the heater is a great example of German engineering.

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

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