Temperature Contradictions

HI All.
I have an 87 litre freshwater aquarium & I'm trying to achieve a steady 24-24.5c temperature.

I currently have two 100w heaters in place. And a digital thermometer with an internal sensor at about mid depth.

According to this thermometer these heaters are producing a water temperature of about 24c. But I have had to set them each at about 30c to achieve this.

I'd started to wonder if the thermometer might be out. So I bought a cheap stick -on-the-glass strip thermometer as some form of independent yard stick.

Whilst I believe these are not that accurate, it reads the temperature as 28c - too hot for some of the tank species.

Does anyone have any idea what might actually be going on in there. And which, if any, reading I should trust?

Thanks as always guys.

 

Sometimes the heaters are off in terms of calibration.

I'm the same way, I shoot for a 76 degree average temp for my community tank. I have two Ehiem Yager 100w heaters. One in the far back right corner, one in the far back left corner. I've had to toy with them a bit to get them set just right. I no longer really pay much attention to the dial on the the top of the heater in regards to what it says it's set at. I trust my two digital thermometers and have just slowly adjusted each heater to where they only kick on when the tank starts to get close to dropping below 76 and turn off before it reaches 77. This took me at least a week or so to get squared away.

Trust your thermometer and maybe get a couple to make sure they are accurate, I've had some off by 1-2 degrees in the past until I settled on the one I'm using now that seems pretty accurate when compared with other digital Thermapen (which I usually use for cooking but also works to check tank temps).

 

Thanks for the advice Tropez. Knowing you've been through a similar process gives me some faith in what I've been doing.
I'm going to go for that 2nd digital therm as you suggest.
My fish seem to be doing well. So I guess I'm not far off.

Sent from my SM-J510FN using

 

If you want to see how accurate your thermometers are, try setting them in ice water for a bit and see what they read. If they doesn't show 0C/32F after about 5 minutes, you know it's off and by how much.

I invested in some temperature controllers designed for home brewing as an extra layer of redundancy for my aquarium heaters, and I sleep a lot better because of it.

 

Thanks for chipping in Briggs. Good to know an easy method for checking!