Mercury or Digital Thermometers?

[Irishman]

I have my other breeder tank set up with an Eheim heater in the DT and a small 10 gallon heater in the sump. I have both mercury and digital thermometer and they're off from the each other by five degrees. Which one do you all trust more? I don't remember needing to calibrate the digital ones.

 

[that0neguy1126]

I'd trust the Mercury one. I use both. a mercury one floating in my sump and a temp probe in my apex.

What digital one are you using? if its plugged into a controller there should be a way to calibrate it. If its just a cheap digital one I think most of those are +/- 3 degree's.

 

[Irishman]

Just the basic ones you see all over the place. I attached a picture of it.

 

[rjl45]

Mercury, or alcohol will be more accurate than that digital. I bought 3 of the digital, under 2 brand names, all 3 had varying temps by up to +/- 3 degrees. I keep my mercury thermometer in the back, for more accurate temps and pull it out from time to time for accurate checks, and use the digital for a quick check because it's much easier to access.

The key to the cheap digital thermometer is to keep a good battery in it and it should consistently read a temp. May not be a correct temp, but close enough for reference.

 

[rjl45]

Oh, one more thing... The digital tend to read low more often than not, so be careful to avoid cooking your corals. One of mine reads 76, with mercury reading 78.