Why am i having bother setting temperature

[Country joe]

I have a Fluval and jewel thermometers, when I set them for 24c one ended up reading 26.5, the other 25.8, I have now set them to 23c and they are reading 24.8 and 25.8 why are they so out, the tanks are in a non heated bedroom.

 

[MattW]

IME I find most heaters aren’t 100% accurate which is understandable. Of course there’s many factors that can alter temperature. Lighting is one. Room temperature can impact the overall temp. Having an aquarium with a lid can insulate a tank impacting the temp. When I had my paludarium the non aquatic part was always warm when I took the lid off which I’m guessing was down to the humidity.

 

[Essjay]

Heaters are notoriously badly calibrated. The way to use them is not to set the dial to the temperature you want but to set it to whatever number on the dial gives the temperature you want, as measured by a reliable thermometer (not one of those stick on the outside lcd strips which change colour)


It's not just aquarium heaters. When my cooker needed a repair, the chap told me that if an oven thermostat is replaced, you have to learn how to use the oven all over again as no two thermostats get the oven to the same temperature.

 

[GaryE]

I have a bunch of high quality heaters that don't respect the numbers on their thermostats. One gives me 23.6, no matter what. One gives 25c. One goes to 28 if I set it for 22.
So I put painters tape on the cords, mark what temperature the heater insists on being at and use it accordingly. Heaters are expensive, and very often poorly made. That works even for the expensive ones. In the past, they killed a lot of fish here by sticking in the on position or overheating water. I now only use eheims and fluvals, and I haven't had that happen for a long time.
If I kept fish that generally needed heaters (most of mine don't) I would invest in electronic controllers. I've learned that lesson. I have my tanks in a warm room now, so I only run heaters for one or two tanks, and for breeders. I watch them like a hawk. Never trust a thief, a junkie or an aquarium heater.

 

[Essjay]

When I bought my Juwel tank in 2006 the heaters they supplied back then did not have numbers on the dial, just a + and - to show which way to turn the dial. The only way to set the heater was by was by trial and error, adjusting the dial till the water temperature stayed at what you wanted.
That's still how I set heaters.



I've been lucky - when my heaters have failed, they've just stopped working so the water gradually cooled to room temperature.

 

[Magnum Man]

I personally think, that unless you are specifically trying to breed something challenging, we worry about the temperature too much… no matter the body of water our fish came from, there is like at least 10 degrees difference, between shady spots, and those in full sun, and the various depths of the water, and between rainy season and dry seasons, and natural air temperature changes of the various areas… then the differences in heaters, as well as thermometers, would drive the control freaks among us, crazy… I may try to make adjustments sometimes, but I look at those as generalizations, rather than to a specific exact temperature

 

[TNG]

Eheim heaters have a dial for heat setting and another one for calibration or adjustment, but adjustment can only be made up to plus or minus 2 degrees C.
If it’s set at 24C and the thermometer reads 26.5C, you can move the calibration dial to make it read 26C. It’s recommended to let the heater settle for a couple of days before adjusting it.

The thermometer I use for calibration is one from a photography shop. It's a long glass tube used for developing old-fashioned photos, the most accurate one you can get.

 

[MuddyWaters]

When I bought my Juwel tank in 2006 the heaters they supplied back then did not have numbers on the dial, just a + and - to show which way to turn the dial. The only way to set the heater was by was by trial and error, adjusting the dial till the water temperature stayed at what you wanted.
That's still how I set heaters.



I've been lucky - when my heaters have failed, they've just stopped working so the water gradually cooled to room temperature.

This is probably the most honest approach LOL- I mean, look at that dial- how are you supposed to hit a specific number on that thing anyway? Now, the digital ones, on the other hand....

 

[MaloK]

I only have 1 heater in all my life that was exact, well 2, but they where same brand and model, one was sold with the tank I was using it, the other is in my current shrimp tank. Even after 25 years, it is still the most precise piece of gear I ever had.

So, If you see an old Fluval Tronic Gold or Silver in a garage sale, Don't be surprised if they ask a good price for it. They are extremely durable and very stable and absolutely reliable. I regret selling my second one.

 

[GaryE]

There are situations where an exact temperature is important. Sex ratios on fry can be temperature dependent, as 26c will give different results than 24 or 28.
There are also fish whose growth rates are affected by digestive enzymes that need exact temperatures to function properly. That's a new area of research, sparked by the need to understand what will happen as temperatures rise. A lot of fish will inhabit one stretch of a river, but aren't found at lower elevations where the water's warmer, for example.

But those are problems specific to fish breeders, or to keepers of a few species (as far as we know until now). Most of us have some leeway with our fish, and most of us overheat our tanks horribly. It's funny, it seems like keepers of rams or discus want to keep their fish cooler than they need based on nature, and for the rest of our fish, we want to keep them too warm. If you can't trust your thermostat on a heater, but it's consistent, then only get fish that are happy at the temp you have.