Heater temp is different from thermometer?

HI All,

So I just got a Fluval 240 tank up and running and I'm seeing a difference between what the tank heater is saying and my tank thermometer is saying.

The tank has been running about a week now so a bit confused

Could it be because of the two big lights also raising the temp?

Thanks,
James

 

Welcome to Fishlore.

As heating is affected by all heat sources, this is very common. Room temps, lighting, even the amount of surface disturbance affect tank temps.

 

Most aquarium thermometers are not very accurate.
They are usually a degree or two off actual temperature.

 

Also, where is the thermometer placed? Warm water rises, so whether you place the thermometer at the top or at the bottom will make a difference.

 

Welcome to Fishlore.

As heating is affected by all heat sources, this is very common. Room temps, lighting, even the amount of surface disturbance affect tank temps.

Most aquarium thermometers are not very accurate.
They are usually a degree or two off actual temperature.

Also, where is the thermometer placed? Warm water rises, so whether you place the thermometer at the top or at the bottom will make a difference.

thanks for replies! the thermometer is at the far end of the tank, right in the middle.
I had it in a smaller tank before and it matched perfect with that heater. It was only a 60ltr tank though

 

My heaters are off by 4 degrees in my bigger tanks. I just set the heater by leaving ot off for 30mins, then turning the dial until it comes on, leaving it until it reaches the temp I want, and then turning the dial the other way until it goes off. Then my heaters are set.