Question Resun 100w Aquarium Heater


Well Known
Reaction score
I have a 100w Resun in my Ciano Aqua 80 aquarium, it came as part of the "plug in and play" setup.

I am just wondering if anyone else has experienced a backward heater?

When I first got the aquarium and installed everything, the heater seemed odd. I set the thermostat to the indicated temp on the side of the heater as normal but for some reason, I couldn't figure out why the temp was lower than the chosen setting, it just wasn't reacting as I expected it to

So I took it out, checked it over and started having a bit of a fiddle with it and discovered something quite unusual (to me, anyway)

On the top of the heater there is a two way arrow......goes from narrow to you might expect that turning the temp setting towards the broader end of the arrow, the temp setting would rise and vice versa turn it towards the narrow end of the arrow, the water would be cooler

My Resun is wired completely reduce the heat you turn it towards the broad arrow, to increase the heat you turn it to the narrow arrow

My aquatics supplier has said that they will replace it as faulty but for the time being I am holding off on that since I finally got it to work and remain stable and I figured out that although the setting control is backwards, its fine, its not causing any issues. That said I will probably upgrade to a more well known brand later on, sooner if needed but right now its working fine albeit backwards.

Has anyone else had weird experiences with the Resun 100w heater like this?


Reaction score
More than 10 years
Hi, I also had a Ciano tank (100) lovely tank but in my experience the equipment let it down, I changed both the filter & the heater in the end.

New Threads

Similar Threads

Follow FishLore!

FishLore on Social Media

Online statistics

Members online
Guests online
Total visitors

Aquarium Photo Contests

Aquarium Calculator

Top Bottom