Temperature swings

[jmags080307]

My temperature has been swinging between 76.5 and 78.3 the past week with my eheim heater. Today I co.e home and it's 80.3. Should I attempt to recalibrate it???? I have a eheim in my other tank and it stays consistently between 79.0 and 79.6.

 

[mcarroll]

How and where are you measuring the temperature?

Where is the heater?

 

[jmags080307]

I have a digital temperature probe and a regular glass thermometer attached in the tank and they both read 79.4 right now because I turned off the heater. Tried to recalibrate it and it's still on. The red dual is turned to 79 and so is my blue dial. God I hate this thermometer! Heater is in the back of the tank.

 

[Joey waid]

Is it big enough?

 

[jmags080307]

Yeah. It's a 300 watt in a 40 gallon and 20 gallon sump.