I just got a new stick-on thermometer for aquariums and put it on the table before i use it on my next batch... but i noticed it seems to always show 21/22 degrees, even when I "think" the room temp is much lower than that. Or at least the room temp should be changing because today is much colder than yesterday, but still shows 21/22*C. I put it against my arm and it goes up to the 30s but I don't know how to make sure this is working. Will do more damage than good if I find out it is not. Any suggestions? I dont have any other thermometer to compare obviously.