Odd Temperature Swings

[pmarsh44]

I must be missing something obvious, hoping someone can point it out to me.

I have two tanks next to each other. One with about 14 gallons total volume between tank and sump and the other an AIO 34gallon.

The temp on the smaller tank is much steadier whereas the AIO the temp drops much faster. The Temp probe in the AIO is in the first chamber and the heater in the last.

You can see even in the on this chart the Blue being the 14g and the orange being the 34g.

Both have a similar amount of turnover, and I've calibrated with a high accuracy thermometer.

Just at a bit of a loss as to why the larger volume of water seems to fluctuate so much more.

 

[Auquanut]

Are you using the same temp controller on both tanks?

 

[ShepherdReefer]

I have a 50-gallon tank with about 25 +/- in the sump using the BRS titanium aquarium heater system set on 77.5 degrees F. My tank fluctuates between 77 degrees F and 78.1 degrees F.

 

[pmarsh44]

@Auquanut yup, both hooked up to my Apex Jr. I swapped the temp probes between the tanks to make sure one hadn't gone bad.

I also moved the heater in the AIO out of the last chamber into the actual tank, down towards the bottom opposite the intake overflow. No change.

I mean it's not the end of the world, if I hadn't set up the second tank I would never have known. But now I'm just so confused!

 

[Auquanut]

But now I'm just so confused!

Me too.

 

[ca1ore]

Two possibilities .... are both tanks glass or acrylic? Acrylic insulates better. Temp loss is a function of surface area to volume ratio .... not just volume.

 

[Spieg]

Agree with ca1ore, surface area can make huge difference. Could also be that one tank heater may have more watts per gallon than the other. Also, could be environmental differences... maybe one gets more direct sunlight than the other or one sits closer to a vent or open window?

 

[Brian_68]

For me I had a new Eheim Jager heater and the temperature would swing 2 degrees from heater turn on to off multiple times a day. Replaced it with the same brand heater and it now swings only 0.25 degrees, same aquarium go figure. Minor equipment differences even the same brand can introduce these irregularities as well.

 

[pmarsh44]

I'm thinking maybe it is surface area.

One is 20x20 and the other is 24x9.5 with the sump that is in a closed cabinet so there's little movement over that portion.

The larger 20x20 also has a MP10 so maybe the combination of the extra water movement overall and the surface area is enough to drop the temp faster.

I am going to experiment with adding more water movement to the smaller tank.

Oh and they both have Finnex 100 watter titanium heaters that are only a few months old.

Thanks for all the ideas, always something new to learn in this hobby!

 

[pmarsh44]

For any future readers, the difference in temp swings was due to rate of flow.

Adding more flow to the second tank must mix things up enough to make the small tank mirror the changes in the larger tank.

Thanks for all the input and ideas!