Eheim Jager Thermostat Aquarium Heater

Installed a 100 Watt on a new 39 gallon tank, set it to 80 degrees, and so far it's been keeping it perfectly at that temperature. It's only been a few days but I'm impressed with the ease of installation and how well it works. Nice and cheap and does what it should!

I ordered two 100 watt heaters and one was not functioning properly (kept turning off before temperature reached). I emailed customer service on a Sunday night and they had a replacement in the mail Monday morning shipped overnight free of charge. It’s hard to find that kind of customer service in 2021. Big thanks to Chewy for that and while yes one heater was messed up, no product in life is going to be 100%. These things happen. I’m very pleased overall.

I’m sure the product would do it’s job if it worked. I set the heater up to 79 and it jumped my temperature over 85 killing two of my fish due to extreme temperature change, I immediately took it out and started messing with the temperature, I found out the red ring that moves the temperature level it’s working properly so as an example if I have set it to 71 it’ll get up to 77-78, I tried to play with the temperature again to try and get it working while I get a new heater (I need one due to cold area) and it wouldn’t even turn on anymore. Will try to return.

I was expecting a working heater but it wouldn't even turn on...anyway I could get a refund?

The biggest flaw I had which made me give up on this heater is the fluctuations are too high, it goes from 74 -80.5 and its set at 78 so it wouldn't be the best option for a reef tank. Chewys service was outstanding though.

First things first, turn the temperature down, and wait. It's important to calibrate the heater before you set it or assume that 77°=77°. I found that the heater is much hotter than the calibration it comes with, and seeing the other comments I would say it's safe to assume that they are mostly all this way. You will need a separate thermometer to calibrate the heater. This is an easy fix, just follow the instructions provided! My 1 complaint is that this heater is very bulky. I thought the glass would make it seem more discrete but I may need to look for another one considering I have a 5 gallon tank. (recently added mopani wood causing the tea-colored water)

I bought this heater 3 months ago and right off the bat I wasn’t happy it always fluctuated 1-5 degrees and now just recently I checked my temp and it was 72 degrees. It just totally stopped heating even though the light was on!

The heater itself works great, however it was missing one of the suction cups. I know that sounds minor, but it didn't want to stay submersed without it. I was able to make a suction cup I had work.

After I purchased this heater and noticed the aquarium seemed a lot warmer than what my other aquarium is (set to the same temperature, different heaters) I brought out a thermometer and found out that this heater is holding the tank right where I want it, vs my Fluval E’s holding the tank 6 degrees low. Here’s where it’s lost the star; the knob is quite difficult to turn at times.

I’ve been using this heater in my 10 gallon betta aquarium and it works wonders! The only issues I have experienced thus far is the turning of the temperature knob is rather hard, you have to use a lot of pressure. Another issue I have seen is that the temperature set on the heater doesn’t match the number on the knob at times. Other than that, it’s slim, holds temperature exceeding well, and is better than any other heater I have used in my years of fish keeping!