Submersible heaters

Over the years, I’ve used various brands of submersible heaters – Eheim Ebo Jager, Hydor, Aqueon, Marina, and Fluval among others. This post isn’t a review nor does it contain any kind of personal heater ranking, however I want to express my overall satisfaction with a particular brand/model.I’ve grown quite fond of the Fluval Digital E series by Hagen. There are multiple reasons for my attraction to and satisfaction with this heater, which are listed below in no particular order.


  • The glass heater resides in a plastic guard, which offers significant protection against large, rowdy fish.

  • The heater has a built in LCD digital temperature display that is easy to read.

  • The temperature settings are in 1/2 degree increments, which will appear on the digital display.

  • The mechanism for changing/setting the temperature is a lever that only requires one hand to operate, unlike other heaters with a dial that, over time, requires two hands to adjust.

  • The temperature display can be set to centigrade (C) or fahrenheit (F).

  • The display utilizes colors to quickly identify temperature ranges - green (safe temp), red (high temp), blue (low temp).

Of course, the most important aspects of a submersible heater are its dependability and accuracy. I’ve owned four of the E series and, to date, I’ve only had a problem with one. Fortunately, it was faulty right out of the box.

The temperature adjustment lever is at the top of the heater, which makes adjusting the temperature really easy and, if you mount the heater vertically, the lever can protrude above the water line allowing you to make an adjustment and stay dry doing it. Also, the colored display allows you to quickly notice a problem with the temperature, especially in the dark.

A word of caution, however. Even though these heaters have been reliable for me, I believe in redundancy. For this reason, I keep separate thermometers on all my tanks and I would encourage you to do the same if you use this heater or any other with a built in temperature display.


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