# How to read a stick on thermometer



## Shanna

The 76 degrees on the stick on thermometer is green and the 78 is brown. Which is correct?


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## froglady

Well I go by the brown. on mine.hope this helps.


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## Sj45

I don't like stick on thermometers if I remember right, it's not the temperature where the number is, the number corresponds to the line below it.

I have digital thermometers and love them, here is a link.

Aquarium Water Temperature: Coralife Digital Thermometer


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## daisycutter

i would go buy the small in tank kind (floating with a sucker)there much better than the stick on ones which im still convinced give you the temerture of the glass not the tank


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## Mikaila31

Now that you mention it. I don't know which one to read. I know stick on's are not the best, but I don't feel like buying one of the digital "exact" ones. Temp can vary. 76-81 degrees Fahrenheit. As long as the colored bars on the stick on's are between those numbers I'm happy. If I think something is up, I can test the temp with a digital meat thermometer........


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## Tyyrlym

That Coralife digital is not reliable in my experience. It's overly sensitive and inaccurate. I've found a lot of people with similar issues. I highly recommend getting the simple mercury style with the suction cup.


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## JohnnyD44

Tyyrlym said:


> That Coralife digital is not reliable in my experience. It's overly sensitive and inaccurate. I've found a lot of people with similar issues. I highly recommend getting the simple mercury style with the suction cup.


thats what I had....i didn't feel the readings of the stick-ons were very reliable, seemed to flucuate too much


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## Byron

I tend to find the stickon to be about one degree higher than the actual temperature. On my 90 I have two of them (one on each side glass), and the Eheim filter has the heater included and a digital temperature indicator and both stickons are consistent with each other and always one degree warmer.

However, I have had ones that clearly were out by more. Right now I have Marina which seem to be accurate (as above). On these the green is the temp.


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## Tyyrlym

There's a few issues with the stick ons. The biggest being that because they are not directly immersed in the fluid they have to be calibrated to read the temp of the glass and correlate that to the temperature of the water in the tank. What that means is that if your room and tank are both at the temperatures the thermometer is calibrated for, and the tank material is the same and the same thickness as it's calibrated for the stick on will work. The problem is that it only works for one particular combination of variables. If any of them differ from what the stick on is calibrated for it won't read the correct temperature.

The big difference between a stick on and one of the mercury style ones is that the mercury style is immersed in the liquid its measuring and quickly settles to the same temp as the tank. There's no guessing or assumptions to be made. The thermometer is the same temp as the tank, period. No matter how cold or hot it is, no matter what the tank is made out of or how thick it is it will read the same.

In the grand scheme of things though... it doesn't really matter. Most tropical community fish come from lakes and rivers and they deal with daily temperature swings. A perfect rock steady temperature is not required. So long as the temp stays within a few degrees of 78 they'll be fine. A stick on will get you in that ball park. Personally I want to know exactly what the temperature is so I use mercury style thermometers. Stick ons will do ok since the exact temperature isn't strictly necessary. If 76 and 78 are both lighting up split the difference, call it 77 and you're fine. The margin of error with a stick on is probably +/- 2 degrees anyways.


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## froglady

Im going to start using the glass ones again. the stick on ones are hard to read. I need to know exactly the right temp. my fish are worth it.. as is everyones..


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