Unfortunately very imprecise temperature display

What should a thermometer afford all the first place? Exactly, show the right temperature! I think that one can expect. The part of Jewel looks smart and does well in the aquarium. Can be fastened well and permanently (for me more than a year in the same place, without that something would slip or could even completely dissolved).

AAAAB: and I am unfortunately come only now, because I'm probably too trusting in the quality of gem (was!). The temperature indication seemed to me a little strange and not quite understandable, therefore, I have now checked it with three other thermometers of different types. The direction indicated by the jewel-part temperature was more than two degrees above the other. Two degrees inaccuracy are just too much, just a Digitalthemometer indicating even tenths of a degree (ha ha ha). In the aquarium, such discrepancies can decide over life and death of the inhabitants before. Sorry, but as it gets!