Question External Vs Internal Thermometer Accuracy

Victoria99

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Which on is better? Which is more accurate?
Temperature strips that you stick on the side
of your tank (outside) are pretty dang cheap, and from what I've heard, very accurate. I have a 48" tank. Clearly, a thermometer on either end is good, so I can reference heater placement and fish comfort. Needing to buy two and having used the strips in the past, I grabbed myself one of those. But I figured an internal one would be more accurate. The internal one is an old fashioned one (with the red stuff in it) with a suction cup, and was about half the price of the strip ($1.50 vs. $3 or so).
I placed them on opposite ends and noticed that no matter what, the internal one always read about 1 degree (Fahrenheit) higher than the strip. After about a week and a half, I moved the internal one next to the external strip. It was STILL one (to 1.5) degree higher.
Which one is accurate?
Is there another way to check the temperature so I can figure out what the water temp really is?
 

Pat93

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If you really wanna get crazy they have digital directional thermometers that will tell you what the temperature is and you can move it around to know exactly the reading.

You can also get an under the tongue thermometer and I think that would be accurate for just a quick check but, I’ve never done it but I don’t see why it wouldn’t work

As far as accuracy goes for most people an external would probably do fine because it’s really just so you don’t accidentally boil or freeze your fishy friends but and internal will always be more accurate if your just asking which one is more correct in your situation

If you wanna keep parts of the tank warmer or cooler then my tips would be more (or less) incandescent lighting and or messing around with water flow to and from the heater
 
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Victoria99

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If you really wanna get crazy they have digital directional thermometers that will tell you what the temperature is and you can move it around to know exactly the reading.

You can also get an under the tongue thermometer and I think that would be accurate for just a quick check but, I’ve never done it but I don’t see why it wouldn’t work

As far as accuracy goes for most people an external would probably do fine because it’s really just so you don’t accidentally boil or freeze your fishy friends but and internal will always be more accurate if your just asking which one is more correct in your situation

If you wanna keep parts of the tank warmer or cooler then my tips would be more (or less) incandescent lighting and or messing around with water flow to and from the heater
Yeah, I really just wanna know which one is most accurate. I don't have a digital thermometer, and I don't think I should really spend my money on that of all things, hahaha. But maybe I could try the under the tongue kind and see what happens.
 
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Victoria99

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a 1.5 degree difference won't cause any harm.
Yeah, I mean it's not that I'm concerned about the temperature difference. I just wanna know what's more accurate. Ideally I want it at 78°, although I'll be getting some fish in the future that might like it a little lower.
 
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