Cobalt heater not working properly?

[I<3Reefer]

I have a cobalt Neo ther, 25 (for up to 6 gallons) on my 5 gallon. I had it set to 78 and had a basic thermometer in there and it said 78.... I added a digital thermometer and it's been readin 80.5 degrees.... which is correct? I dropped the heater down to 76 and it still reads 80.5.... Could it be my stock light heating up the 5 gallons? It's odd, even after the light being off overnight for 11-12 hours it still reads only as low as 80.1

 

[Crabs McJones]

I have a cobalt Neo ther, 25 (for up to 6 gallons) on my 5 gallon. I had it set to 78 and had a basic thermometer in there and it said 78.... I added a digital thermometer and it's been readin 80.5 degrees.... which is correct? I dropped the heater down to 76 and it still reads 80.5.... Could it be my stock light heating up the 5 gallons? It's odd, even after the light being off overnight for 11-12 hours it still reads only as low as 80.1

What is the ambient temperature in the room you're keeping the tank and how much surface agitation do you have to promote evaporation?

 

[NY_Caveman]

I would trust a glass thermometer over a cheap digital one.

 

[joec]

I have a cobalt Neo ther, 25 (for up to 6 gallons) on my 5 gallon. I had it set to 78 and had a basic thermometer in there and it said 78.... I added a digital thermometer and it's been readin 80.5 degrees.... which is correct? I dropped the heater down to 76 and it still reads 80.5.... Could it be my stock light heating up the 5 gallons? It's odd, even after the light being off overnight for 11-12 hours it still reads only as low as 80.1

Do an ice water test and find out, but follow the instructions carefully. One or both could be wrong

 

[ZoWhat]

Digital thermometers can be as much as +/- 3 degrees or more OFF in accuracy..... even more if you have a bad one for the factory.

The factory where these are made are mfgr'ed like popcorn kernels. When the factory line is setup, they make like 50,000 to 100,000 of these at a time. They only pull maybe 0.1% of them off the "line" to do a QA test on them. Even then, they allow a +/- 2 degree swing.

Best way to measure "real" temp is to get a glass thermometer from Amazon that's lab-grade with a test accuracy of +/-0.5 degrees....but you're gonna pay like $30+ for the thermometer.

 

[I<3Reefer]

Ok I'll do that, my thermometer was also $4 on amazon, maybe it just sucks... Not sure if there's specifically brands which are more accurate?

 

[I<3Reefer]

Ok, I may do that, I'm wondering if I should just trust my heater more too. The cobalt wasn't cheap, so I gotta feel like it's accurate to some extent. And it matches up with my cheap suction cupped glass thermometer. I don't mind paying $20 for a thermometer though, heat consistency is pretty important right? Any brand recommendations? or a link?

 

[joec]

You don't need a new thermometer. You can determine how far off your thermometer is with the ice water test and then adjust everything to the desired temp.

Ice water is 32 degrees. If your therm tests at 35 degrees in ice water for example, your thermometer is reading +3 degrees above real temp

 

[408Dartfish]

I would trust your heater more also. I have a 10$ dig thermometer it’s about 3 degrees off which is about normal for those. Dustin

 

[NY_Caveman]

My Cobalt heaters (25, 50, 75 and 150 W versions) are all pretty accurate in my experience. My Ink Bird temperature controller with a probe and digital readout is about 0.5 *F low. Glass thermometers I have found the most reliable. The cheap digital thermometer I tried was useless.

 

[Ferrell]

I wouldn’t trust either the heater or the digital. My heaters are all off 2 or 3 degrees and my digital thermometer was off 4.
I’ve got several $20 thermometers that I use and take an avg. They are usually within a degree or two of each other.