Unexpected Temp Rise

[scenicad]

I just added about 50 lbs of live rock to my 100 lbs base rock in my 72 gal tank. I don't have any fish yet, but in prep for the LR, I've been running the PH's, and even kept the lights on (regular fluorescent, it'll be a FOWLR). The books I have said that 75 deg. is the a good temp, so I've kept the temp at 75, and it's been very stable. Until I added the live rock. Now the temp is at 80, and the heater hasn't been on at all.

What's happening?

Also, the 10 gal QT is running right beside it, and it's temp is stable at 75. My apartment surely isn't at 80.

Would the LR be adding this heat? It does have a lot of life on it -got from LR.com, but I can't imagine it would raise the temp like that. But that was the only change to the tank. In fact, it's still at 80 even after the lights were off all night and my apartment is cooler.

 

[nickthapainter]

The LR wouldn't have added the heat. However it did displace some water -- tank capacity went from 72 gallons to around 50 total. Thus your powerheads and lights are heating up a lower volume of water (temp will rise quicker).

5 degrees seems like an awful high increase though with only the PH's on at night.

I'm sure others might have some better ideas/theories.

 

[scenicad]

Thanks for the suggestion, but the water level wasn't high enough for the LR to displace any out of the tank. In fact, I'm going to have to add about 5 gal more today to bring it up to the top.
I even took the thermometer out of the QT and put it in the main tank to make sure it wasn't the thermometer that was bad.

The only other factor that is different is that the skimmer is on now too. Could the Mag Drive 3 be generating that much heat?

Has anyone else encountered this?

 

[nickthapainter]

The skimmer pump will add some heat of course -- maybe 1 or 2 degrees at the very most.

You could try running the mag3 externally and see what kind of change that makes.

 

[cmor1701d]

Most people run their tanks at 80-82 anyway so I wouldn't worry too much about it.