Which should I trust? Thermometer or heater?

I ju realized that my betta fish’s tank heater was unplugged this week, he’s acting fine and I plugged it in again. But now my thermometer says it’s around 72 degrees fahrenheit but my preset heater that is set to 78 degrees says it’s at the right temperature. Which should I trust? Should I be worried? I’d there anything I should do?
Sorry for all the questions, any help i’d appreciated.

 

I tend to trust thermometers over heaters. Also why i get adjustable heaters. Heaters are often off a few degrees.

 

Good to know, should I just wait and let it heat up?

 

You can. In the meantime i would probably start shopping around for an adjustable.

 

Do you have a digital thermometer, even like a probe type meat thermometer? Most of those are relatively accurate and can give you an idea of what the water temperature is.

 

I can’t get one until tomorrow, do you think my fish will be ok?

 

I think behavior is the key. You say he is acting fine, and the tank is probably at least 72, so he should be fine. Remember, many (unfortunately) are kept in tiny, unheated bowls or whatnot.

 

I actually got him from my friend who had him in that situation

 

Nice rescue- that's awesome. He's a lucky betta.

 

Thank you! He’s definitely happier now
Does anyone have any recommendations for an adjustable heater because I can’t find any that aren’t $50+ are they really that much? My tank is 5 gallons if I forgot to say that earlier.

 

Thank you! He’s definitely happier now
Does anyone have any recommendations for an adjustable heater because I can’t find any that aren’t $50+ are they really that much? My tank is 5 gallons if I forgot to say that earlier.

I suggest the fluval m50. I got mine for 20$ on Amazon.

 

Thank you, i’ll look into that

 

I’m stumped, because my thermometer says the water is 72 but it feels 78-80. I tried taking it out of the water and putting it in warmer water to see if it changed and it did, so am I just wrong and the heater needs replacing?

 

There are ways to test the calibration of a thermometer. Crushed ice with a little water should temp 32 degrees, boiling water is 212. If you look around on the internet, you might find a way to check the accuracy of your themometer.