IS THERE A HEATER, THERMO-CONTROLER, OR COMBO UNIT THAT SHOWS TRUE TEMPERATURE?

[EASTERN INDIGO]

I have found the BRS heaters and controller to be very accurate. Been Using them for 2 years now and never had an issue. I check them every couple of months with the ice test and a professional chef thermometer.

Pardon my ignorance. What is the ice test?

 

[EASTERN INDIGO]

A Bulk Reef Supply analysis of all the heaters showed that the Cobalt Neotherm had the most narrow temperature range of any heater, I think it was around one degree +/-

Tried it and at first loved it, but it jammed up relatively a short time after buying it, and that was in freshwater. As a matter of fact, I think it happened with two of them. In salt it would have gone faster. I'm looking for overall dependability.

 

[Sleepydoc]

Pardon my ignorance. What is the ice test?

An ice bath of pure water will stay very close to 32º F/0º C and you can use that to calibrate a thermometer. Of course, that assumes the thermometer has a linear response curve and remains accurate in the temperature range of interest.
There are many links online - below is one I found.

How to Test Digital Thermometer Accuracy with Ice Water | Cook's Illustrated

You don't need lab-calibrated tools to find out if your kitchen thermometer is accurate. This simple test with ice water does the trick.

www.cooksillustrated.com

 

[Sleepydoc]

This stuff is mostly hobby grade equipment .... not lab grade. Aquarium hobby heaters are notoriously inaccurate, all that one can really hope for is some level of precision. I used a couple of inkbirds a few years back and found them to be absolute crap; perhaps they are better now. Something like the Ranco is better. It's designed to operate in industrial applications where accuracy and precision are important.

Exactly this.
I’ve learned not to trust any of the heaters that are out there. The best heater is the one that’s working for you right now. The worst heater is the one that just failed. Often times the only difference between them is a day.

Virtually none of the thermometers we buy will be terribly accurate, nor will they have consistent long term reliability. Even the ‘better’ equipment will have a specified error range of ±1-2º. The best route is to get 2+ undersized heaters for your tank and a separate controller like a Ranco, Apex, etc. Use the controller to control the heaters and set the heater thermostats to turn off a degree or two above your desired temp.