I have noticed my heater and my thermometer dont seem to be accurate. I keep my ambient room temp about 75. My heater set to 78 Hydor theo heater and my thermometer says 82. When i turn off my heater the temp in my tank go to 79-80 tops when the lights are on. The thing is I need my heater on because if i dont have it on my temps when my lights are off slowly drop to about 75 degrees. I guess what im saying is I need to figure out a way to stabalize my temps. I have a biocube. Im guessing i should just keep the heater off during the day and put it on a timer to only work when the lights are off (at night)? Is my heater screwed up? i set the heater to 78 and tank is showing it is 82 and the red light on the heater says it is on shouldnt it turn off when temps are above 78?? Anyone have this problem?