Features:

  • Fully submersible
  • Thermo safey control protects against running dry
  • Will automatically turn off when water level dips too low
  • TruTemp dial recalibrates the heater for precise temperature regulation
  • Made of shock resistant and shatter proof glass for fresh or marine water
  • On/Off indicator light for at-a-glance monitoring
Best quality heater in price range

I have owned 7or 8 Jager heaters over the years and never once has a unit completely failed. The outer glass in dual-layered. What typically happens to me is that this outer glass will develop a leak in 3-10 yrs (sometimes my fault). You get a little water between the two layers and replace as soon as possible. I usually keep a second on the shelf for this reason. Usually I have to dust off the next in line because it's been so long. The dials aren't perfectly accurate. Take your typical glass thermometer from Petco and calibrate. These heaters keep a constant temperature over the long term and click on within less than a 1degree drop. So, be careful calibrating. Have a backup for when it finally goes in many years. Sit back and relax. A tip - if you are someone who needs to change the temp often for whatever reason, buy a separate temp controller that sits outside of the tank, displays the current temp, has a temp probe running to the tank and allows for easy adjustment. That way you can turn the Jager up to the highest temp required or a degree above that and use the separate controller (hydor makes a decent affordable one). Last tip - I've gone the in-line heater route to my Eheims. I prefer the Jager in-tank hands down. However, you can setup an inline and an in-tank (under gravel cable or conventional) to add some redundancy to the system. If one heater goes down - just pull it and your fish don't suffer for a minute. Best, Eric

May need calibration right out of the box

I got the 25W heater for a 5 gallon aquarium with a single betta and snail, and so far it's kept the temperature at a solid 78 degrees with no fluctuations. The heater is longer than I expected, but fit vertically in my tank fine after I dug a little impression out of the gravel. Being a novice fishkeeper, this is my first heater and I was worried that it might burn my betta's delicate fins if he got too close. I was veeery wrong - it's so gentle that he likes to sit right next to it at night and rubs against it regularly. One thing is that right after I got it, my thermometer showed it was maintaining the temperature at 84 degrees rather than the 78 that I had set it to. The directions (which are printed in horrible format in an accordion map style with all languages on the same page) detailed a straightforward calibration process. You unplug the heater, measure the actual temperature in the tank with an accurate thermometer, set the RED arrow to the actual temperature, and then twist the blue ring to the desired temperature. Both of these are really hard to turn and I had to take it out of the tank, but I guess that's good since you don't want it twisting accidentally. After calibration it operates perfectly and I'm very happy.

Excellent heaters made in Germany!

I've raised fish for many years and have to say the Eheim products are great. I have owned this brand heaters for probably 20 years and they have always been great performers. Very accurate temperature settings and very tight control on water temperature fluctuations as long as you install them properly (vertical near water flow). They cost a little more than the bargain brand heaters but are worth every penny. These are made in Germany (not china) and will last you a long time. I would recommend them to anyone. Nothing is worse than to discover your bargain priced heater failed and killed off the valuable fish in one of your aquariums! If I had to give any negatives about the heaters, I would say that the color is a bit loud. They used to all be green with a green cord and they blended really nicely with the décor in a well laid out aquarium. Now the blue color with white lettering and red ring is not as visually appealing but I would not take away a star for that. I've included a pic of the heater in my tank so you can see what they look like in real life. Oh and this is not one of those free items in exchange for my review... I paid for this heater!

splurge for this, it's worth it

My 10yo daughter and I are just getting started with fish. We live in a cold climate and wanted her tropical fish to have the right temperature when the thermostat is turned down during the day. Occasionally I come home for lunch, and this heater has no problems holding the temp 12 degrees warmer than the rest of the house during the day. It is easy to set for a precise temperature, and in the last few weeks I have never seen the tank temp even vary at all. Basically you plug in the heater (once it is in your tank), check your thermometer over the next hour for the actual temp of the water. Then you turn a ring on the heater so the arrow points to the exact temp. There are degree markings to raise or lower your tanks temperature. To start with, I set the heater to 74degrees. It actually settled at about 76. After adjusting the setting ring, I turned the tank up to 78 and it has held steady at 78 ever since. It seems like all of the smaller "preset" heaters have some that work great and others of the same model have major issues and fry the fish. This German made heater has a reputation for lasting 15+ years. This 25watt heater is good for 2gallons up to 7, the 50w is for 7 gallons up to 16 gallons. Buy this heater and you will have peace of mind that your fish are warm and safe!

Rad heater bro

I was wary of switching to a different brand of heater. I previously used Visi Therm Stealth by Marineland, but I've been without an aquarium for a few years now. When setting up my 29 gallon tank, I found that brand no longer had high ratings. From what I read, they are being assembled in a different place and are now prone to failure. Having read horror stories of hobbyists finding their fish roasted by malfunctioning heaters, I did way too much research on brands before deciding on an Eheim Jäger 125 watt model. The heater has been in use from September 2013, to now, May 2014. It has performed superbly, keeping my aquarium at a very steady temperature. I have never seen a fluctuation of greater than one degree. I love the thermostat on this heater, a dial with printed temperature settings. I think mine is off by about two degrees, but it's a non-issue that is easily adjusted for. I would definitely recommend this heater. UPDATE: it's now March of 2015, and the heater is still working perfectly!

Great heater, big size

As I am sure you already know, this heater is huge. It is about 10 inches tall and fits perfectly into my Finnex 4G. The minimum water level is not too high either. The one I bought through Amazon actually broke on me and the heater was stuck ON. Luckily, I am cycling my tank and it didnt harm any fish. Returned it and got a new one at a LFS and its great! Included instructions are pretty lame, but if you need help figuring it out its simple: 1. turn blue dial to desired temp - 79 degrees for example 2. wait an hour or two 3. monitor temp of water with another thermometer, lets say the water heated up to 82 degrees 4. spin the red/inside dial to 82 degrees 5. turn the blue dial back to desired temp Now your thermometer is calibrated!

Great heater. Made in Germany so it should last a while.

Got this heater to replace a fairly new Aqueon heater whose thermostat went bad. So far I can say that I am happy with this heater. It has heated to within .5 to .7 of a degree of what I set it on according to my thermometers. The heater comes calibrated out of the box but if you look at the instructions it says to move the blue temp ring on the temp you want to set it on. Wait a day or two and confirm with an ACCURATE thermometer that your water is in fact that temp. If not, move the red ring to the temp that your thermometer is currently showing and then move the blue ring to the temp you want to be at. This should be enough to get you into that range. The heater appears to be of good construction and it isn't so much bigger in length than other heaters but it definately is bigger in diameter, although that should not be of concern to anyone. If you have glass in your aquarium, the suction cups will hold it. It looks modern and won't take away from the appearance of your tank. The price here on Amazon is also cheaper than Petsmart or other online outlets in my experience.

This one heats perfectly

What a long.................long heater. Be sure you have more than 20-inches to spare for this big boy to fit in your aquarium. It will work both vertically or horizontally. Along with its impressive size is its impressive and accurate heating ability. I upgraded from a 55 gallon tank to a 150 gallon tank measuring 30" tall. The poor little heater that was in the 55 gallon tank was only rated for 100 gallons and it tried so hard to keep my fish warm. He chugged along for 4 days while waiting for this big boy to arrive keeping the water at the bottom of the heat chart for tropical fish. Once I plugged the Eheim heater in it took only 2 hours and the tank was a toasty 78.9 degrees.. Perfect for my little swimmers. This heater cycles quickly and a drop of only .02 of a degree will make this bad boy jump into heater action. The amber indicator light glows quite brightly and the only drawback (if there really is one) is that the heater only glows when heating. Once it has reached the desired temperature, it just hangs there in dark silence. Most heaters glow green when the water has reached the proper set temperature but this guy doesn't. If you have a large tank, this is the heater to get. With a 3 year guarantee backing it up and a very reasonable price you can't go wrong. Just remember that he measures a whopping 20" so he needs lots of room.

Excellent initial impressions. Has consistently even heating and easy to read controls.

I spent a long time trying to make a decision between this heater and the Aqueon 06105 Pro Heaters Submersible Aquarium Heater, 50-Watt. Finally, I presented a question here and on the product page for the Aqueon, asking reviewers which they would choose "today" (it's the end of October 2015 now). Overall, the most resounding answer was to choose the Eheim. Both of the Eheim and the Aqueon have very attractive features. One thing I thought about was that this heater has a 3 year warranty, while the Aqueon has a life-time warranty. Also, this heater is made with glass as opposed to Aqueon's aluminum. Despite that, it seemed that the Eheim had better features when it came to even temp control and easy to access and read thermostat controls. This heater comes pre-set at 80 degrees. After some initial adjusting, I found that it's keeping my 10 gallon tank at 80 degrees with the thermostat set at 75. The weather is a bit warm right now, so I might have to adjust the thermostat as the temperatures get much colder. One thing to bear in mind is that this 50 watt heater is around nine inches in length. That's a lot longer than any aquarium heater I've used in the 50 watt size. I really like that I can easily see the numbers on the thermostat dial. Also, because the heater is so tall, the thermostat dial is very close to my aquarium's surface. All this makes it very easy to set the thermostat without endless fiddling, or worse, having to take the heater out of the aquarium. When the heater is on, there is an easy to see amber indicator light. The two suction cups that affix the heater to the wall are very effective. So far, I'm very pleased with this product. I will update this review as time passes to let you know how things progress. In the meantime, I'm posting some pictures from my initial experiences. Um, not sure what is up with Amazon, multiple copies of my phots keep showing up despite my removing them.

Nicely fits into a 5 gallon Betta tank

i am a very picky shopper, especially when it comes to my pets, and my Betta fish (Nova) is not exception. when i upgraded him to a 5 gallon tank, i spent hours researching every heater that would possibly work for that size. I finally settled for this one and so far after having everything set up for a month, it's doing its job great. Yes, it is a deceptively large heater but once i got it attached to my tank, it fits right in and you can't really notice the size, and my Betta could care less, as long as he can curl around it for his nap time, he's happy. The only factor you have to watch for is that it runs hotter than what you set it as. At first i set it at the normal 78 degrees and it had the water up to 84 by the next morning. I finally got it to the right temp after setting it down to 70 degrees and its been maintaining the tank at a consistent temp ever since. I can't speak of this heater in the long run yet but at least i know Nova will be nice and warm this winter.

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