Okay, so I have a Coralife Digital Thermometer - Digital Thermometer | Coralife Marine & Freshwater Aquarium Supplies
I also have a AA 3008 Digital Thermometer With Dual Alarms - Digital Thermometer With Dual Alarms
I also have a regular mercury-type Aquarium thermometer..
All 3 read completely different tempatures, On top of that there is also a thermometer on my new Finnex HC-0810 Digital Heater Controller.
My Coralife thermometer reads: 78.2
My AA 3008 thermometer reads: 77.4
My mercury-type thermometer reads: 81
My Finnex HC-0810 Digital Heater Controller reads: 78
All 3 thermometers are in the same place about 3" apart inside the tank, while the Finnex HC-0810 is down in my sump.
So how to I test which one is accurate? The Coralife has a Calibrate button, I don't know if the AA 3008 can be calibrated or not.