Heater temperature

[superman]

My tank usually runs a little high in temp (81-82) degrees, although the desired temperature is around 77-80 degrees. Just wondering, if my desired temperature is in that range, what should I set the heater at. Never really gave it much thought because I thought I was getting higher heat from the lights, but the temp is actually higher when they aren't on because the fan I have blowing across the tank is off when the lights are off. The heater is set at about 79 degrees, but this seems it may be too high. So where should it be set so that it kicks on to keep the temperature in the desired range?

 

[bang guy]

If you want to maintain 79 then the heater should be set at 79. Keep in mind that aquarium heater and aquarium thermometers are notoriously inaccurate.
If the tank is at 80F and the heater is on then the heaters thermostat is off. Just set it a little lower to compensate.