| With the amount of flow in a reef system, I'm suprisied that you'd get tempature readings that different.
The first thing I'd do is put both thermometers in the same location and make sure you get the same reading on both. If not, there is a calibration problem.
If you do get the same reading on both, then we have to figure out why the tank is different. I would suspect that the water movement in the tank is not correct, and the changes in the tank reading are caused by the lights comming on or going off. |