Ive a second temp sensor in my Discus tank and it was showing as 26.3c, it should be 28c, I then put sensor in a jug of cold water and its now reading 32.7, is it a faulty sensor? or is there something else ive missed.
The one in my reef tank is working perfectly and keeping constant 26c.
The one in my reef tank is working perfectly and keeping constant 26c.

