Thermometers gone wild! Which one do I believe?!

[SuomiBetta]

Hi there! I'm still embroiled on my struggle to get my 5 gallon tank steady before I add a fish. Since I have a tropical tank I have a heater (Hydor 25w rated for up to 9 gallons) and I recently got an HDE digital thermometer thinking it would be more accurate and precise than my old alcohol thermometer. I currently have the heater set to 75 F. It still turns on (there's an orange indicator light telling me the heater is heating) even though the digital thermometer is reading ~79.7 F. So which one do I believe? Is my heater's internal temperature setting off by 5 degrees or is my digital thermometer too sensitive?

 

[Brookster123]

Believe the thermometer, the numbers on the heater are merely a point of refernece, especially if the wattage is rated for a larger tank.

Sent from my SAMSUNG-SM-G900A using Aquarium Advice mobile app

 

[SuomiBetta]

Thanks! I'm already being driven crazy with the chemistry and I was hoping that I could at least keep the temperature steady.