I set two at the same temperature at either end of a 40 gallon tank and three thermometers attached to the front glass and after facing temperatures that were off by as much three degrees on either side of the tank I finally pumped them up to 85 (no fish, don't worry!) to see what would happen. They're closer together at this temperature (off by about one degree), but I'm still frustrated by the whole experience. Will give it another day or two and see if it straightens out. The whole process is made more difficult by the fact my house temperature is usually a degree or two warmer than what I set the tank at. I have an aqueon pro running in another, smaller, tank that has been spot on for over a year.
Last edited by psych; 08-25-2014 at 01:42 AM.