Two of my thermometers seem to have a mind of there own. Sometimes they will switch to the "out" reading by them self. Always freaks me out because I keep forgetting about that. I got up today and when I checked the temp of my tank, it was below 70! I scrambled to find a heater, quickly tossed it in, then a few minutes later it dawned on me to check the reading again. Heh, sure enough the darn thing wasn't reading the "in" tank temp again. Had to hit the "pwr" button to switch it back to the "in" and all was fine at 78f. I quickly removed the heater.
So my point in this msg is to warn you people that if you see a reading thats way off, check to make sure its still set to read the in-tank temp, not outside temp. That could really lead into a serious problem if thats not noticed and you goto crank up the heater.
btw: no I don't have a heater in this tank yet. The one I grabbed I won't leave in because its got a bad thermostat so it can't be trusted. The tank is saltwater and with both pumps running, it doesn't fall below 76. It averages around 77~78 on its own.