Hydor ETH 300

Heating of my 125G tropheus tank is provided by an Hydor ETH 300 external thermal heater with 300W. These heaters are not cheap - although Petsolutions frequently has them on special - but I absolutely love them! They are superbly manufactured flow-through heaters that are plumbed into the return line from your canister filter to your tank. This makes the heater invisible in your show tank, even if you are not using a sump system but a canister filter. Of course a canister filter with built-in heater would have the same effect, but they can be pricey too, and if you already own a canister filter without heater, or you like to have the two devices kept separately so you have to replace only one part in case of a defect, a Hydor external thermal heater is a perfect solution for anybody wanting to take the heater out of their tank.

I have heard of people using the ETH 300 in tanks of 150G and holding the temperature easily where previously two heaters of the same nominal strength had been needed to accomplish the task. Also, I am using the same ETH 300 heater in a 75G tank, and it keeps the temperature right on target without any noticeable swings. In short this heater seem to be not only surprisingly powerful but also well regulated enough to be usable on smaller tanks. For more user reviews click here.

On occasion, I have forgotten to unplug the Hydor ETH 300 when I turned off the flow and performing filter maintenance. I don't know how draining it when switched on would effect the heater, but it seems as long as it filled with water shutting off the flow seems to have no ill effect on it. Presumably it switches itself off.

In short, if the high purchase price compared to standard heaters does not discourage you, there is nothing not to love about Hydor ETH 300 external thermal heaters!

Hydor ETH 300

Addendum March 2009:

While there is nothing to take back with regard to the quality of Hydor ETH heaters, Hydor THEO heaters receive terrible user reviews on Cichlid-forum, and horror stories about boiled fish due to malfunctions of this heater series continue to pile up! Make sure not to buy a Hydor THEO heater!