Heating - which thermometre gauge is reliable ?

[steeledr]

I have 3 x different readings on my thermometre instruments. The 2 x tank heaters are set at 25 degrees ( usually only 1 is working ) and I am getting a reading of 30.3 degrees with a digital thermometre and a different reading of 29 degrees with a glass thermometre. Which reading is correct? I presume the glass thermometre is the right reading but who knows? My fish appear happy but it has left me confused. Which reading should I go by? Anybody have similar issues or advice?

[Joeburba]

Most of them are -2 or +2 degrees unless you pay $50-100. I would just average the numbers and if its a ebay digital thermometre bin it !!

[steeledr]

Hey Joe, Thank you very much for the advice. I am using a glass Thermometre which appears to be reliable, it says 29 degress and the 2 x tank heaters say 27 degrees so hopefully it is right. The discus all appear to be very happy. Yeah the digital thermometre was from ebay and it was reading 31.9 degrees which seemed really odd, obviously not correct so I have thrown it away.
:D