Eheim Jager Aquarium Heater Review

I got one of the Eheim Jager series aquarium heaters when I was reviewing the Fluval Spec III aquarium.  It’s impressive – if they made it a little bit shorter, I would use it in our main aquarium (the Spec V). I got the 25 watt version (model 3611090), which is plenty for the small volume of the Spec III.  The Jager series heaters are also available in 50 watt, 75 watt, 125 watt, 150 watt, 200 watt, 250 watt, and 300 watt.

Eheim Jager Aquarium Heater contents from box

Eheim Jager Heater: Features and Dimensions:

From Eheim’s literature and from my observation, the Jager series heaters have the following features:

  • Can use in freshwater or marine (saltwater).
  • Fully submersible design, or you can setup with the top out of the water (as long as water reaches the minimum fill line)
  • Adjustable set point, from 18° C (64.4° F) to 34° C (93.2° F)
  • Temperature accuracy to 0.5° C
  • Safety feature to shut off the heater if it is not immersed to the fill line.
  • Ability to correct the temperature calibration (by way of rotating the red ring)
  • Comes with a suction cup mount (removable)
  • It’s got a lamp that indicates when it is heating (located about 1/3 down the glass heating element section.

Eheim Jager Aquarium Heater with suction cup mount attached

I took some dimensions of the heater as follows:

  • Length (total from end to where the cord exits): 243 mm (9.57 inches)
  • Diameter (at the largest point – the blue temperature adjust dial): 36 mm (0.12 inches)
  • Diameter (of glass heating element section): 25 mm (0.98 inches)
  • Length from element end to min water level line: 195 mm (7.68 inches)
  • Depth of suction cup mount (from glass face to furthest edge of blue temp dial ring): 47 mm (1.85 inches)
  • Power cord length: 187 cm (73.75 inches)

length of 25 watt Eheim Jager Aquarium Heater

I purchased my heater in the USA from Amazon.  The dial reads in degrees fahrenheit; I’m not sure, but I suspect ones purchased from countries using SI will have degrees celsius.

Heater Setup and Impressions:

Not much to say about aquarium heaters – they are simple devices and should be easy to setup.  This heater meets that expectation.  It has an adjustment dial to set the temperature where you want it.  It is the blue dial that you see – just rotate it so that the arrow on the red ring points to the set point temperature you want to maintain.

blue control dial and red calibration ring on Eheim Jager Aquarium Heater

One unique thing is the Eheim Jager heaters have a way to adjust the heater if it is not reading correctly.  You do this by rotating the red ring.  You will need an accurate thermometer to perform this calibration (I’ve had good luck with electronic thermometers).  If you have your Jager heater set on 75° F and your (separate) thermometer indicates a tank temperature of 78°F, you would perform a calibration to correct this by rotating the red pointer around from 75° F to 78° F (without moving the blue ring).  There is a guy on YouTube that takes 9 minutes to tell you what I just described in a few sentences.  Aren’t you glad you are here instead of YouTube!

One word of warning that is apparent from this design.  When you purchase this heater, you would assume that it comes from the factory with that red ring set in the proper place (or very close).  There really is no guarantee of this.  The factory might not have calibrated, or you may have purchased a returned heater with the ring rotated previously.  All of this is to say that you should keep a close eye on the heater when you first set it up, making sure it is in the ball park of what you intend. Not that they are helpful at all, but here are the manufacturer instructions.

I have seen some bad reviews on amazon for this heater where it was not performing at all as the user intended.  I suspect that the heater came with poor calibration, or even more likely the user rotated that red (calibration) ring around before they knew what it did, thus ruining the heater accuracy themselves without knowing it.

I have not used this heater over an extended duration, but have used it for quarantine tanks and such.  It has worked great.  I have used it both with a temperature controller and without. It seems perfectly reliable and accurate even when using no controller.

side view of 25w Eheim Jager Heater

I very much appreciate the construction of this heater.  The glass seems thicker and more durable than the competing Hydor Theo heater that I use on the Spec V aquarium. The cord is downright robust – seems prudent to give a heater a good cord to make it efficient in getting the power where it needs to go. I love that it has a full 6′ long cord – rather have too much than too little.


Cost and Comparison:

I think it is reasonable for this heater to be priced slightly higher than some competitors based on the better construction I have described.  Pricing is fairly flat across the rage of heat capacities (all in USD): The 50 watt is around $21; 200 watt is around $32; the 300 watt is around $32.  As a comparison, the Hydor Theo heaters is $ for the 50 watt and $25 for the 200 watt.

The Eheim Jager heaters are very capable and durable.  I love the construction.  If I needed a large capacity, in-tank heater for a larger aquarium, I would probably start with this model in my search.  I will most likely always rely on temperature controllers to drive the heater operation; however, the controls on this heater are good enough to be trustworthy if I needed to operate without a controller.

Use in Fluval Spec Aquariums:

As I alluded to earlier, the Eheim Jager heaters (25 watt and 50 watt) do not fit completely submerged in the Fluval Spec V aquarium – it is too tall.  I suppose if you were operating your Spec V without a top you could arrange the tall Jager heater and have it poke out the top some.  I discuss heater options for both the Spec V and III separately.

This heater fits great in the taller Spec III aquarium. You could suction cup mount this heater inside the display section; however, it’s cleaner to put it concealed in the pump section.  If you do this, don’t bother with the suction cups – just lower it down and let it dangle.

Eheim Jager Heater mounted in Fluval Spec III aquarium

If it touches the flow tube or the glass a bit that’s not a problem. Don’t forget that if you place the heater in the pump section consider performing the flow tube modification.

Eheim Jager Aquarium Heater below lid inside Fluval Spec III Aquarium

I think the 25 watt capacity is ideal for the small Spec III and that the 50 watt will be overkill unless you keep your home very cold.

packaging for Eheim Jager Aquarium Heater

The bottom line is this: The Eheim Jager line of aquarium heaters have a robust build, are accurate, have been reliable in my use, and are a very reasonable price.  If they made one just a bit shorter I’d use it in our main Spec V aquarium.  Highly recommended for those with Spec III aquariums or anyone who needs a good submersible heater.

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