Where do you get the most accurate temp reading from in your reef tank
 

Ok. We all have that "magic" number we like our precious tank to run at temperature wise. Where do you place your thermometer/temp probe to get your readings?

Overflow box. Any water entering the box should be the average of the entire display tank.

Mine is right in the display in the corner. I have one in the sump too. They read the same.

I have tired my overflow box and sump both were similar I keep on in the sump whjere water moves to return chamber

This is a poor location IMO. For two reasons (that may or may not be applicable to your tank)

1. Depending on water height, in a power failure the overflow box water level may be lower and thus your probe out of water
2. Overflow boxes typically get increased light due to there close proximity to the lights, this can lead to higher temperature readings (of course it depends on the overflow design and the speed of which the water enters the box and leaves) and of course light placement in reference to the box, but for me it would be influenced.

I put my probe in the sump,
Also measure my DT temperature with a digital thermometer, the difference was about 0.2....


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My overflow box has a herbie system so the probe is below the water at all times and I use LEDs so virtually no heating effect from the lights (unlike my old MH lights which I replaced about 7 years ago). I've had the probe in the display & the sump and minimal difference. In my overflow, the fish don't mess with it when feeding and I don't have to open up my stand's doors to check temperature. So no, your points are not applicable in my system.

I put mine in the water

Hahaha. Me too!

In a chamber before the heater is the most accurate. That being said I have one in my overflow box and one in the baffle before the return pumps. (Heater is in the first chamber of sump)

I have my probe in the drain chamber which is before the heaters.