Temperature rising with heater turned off ... any ideas?

[olliesshop]

The temperature in my 125g tank has been steadily rising, even with the heater turned off.  The temperature has increased about 1 degree over the last month (BTW I have a very accurate, certified thermometer).  For the last year or more I haven't been able to get it under 80.1 degrees.  Now it's up to as high as 81.1 degrees.  I'd like to get it down to 79 or so.

I was wondering what you all think it might be?  Could it be the canister filter pump heating up the water as it flows through?  I have a pretty old Rena Filstar Xp3 Canister Filter, which I got with the tank when I bought if off Craigslist a few years ago.

Thanks for any help 

[four_by_ken]

Feel the filter, is it warm?

[cranialdisturbance]

Is the tank located by any heat vents? A canister filter just doesn't typically use enough power to raise 125g of tank water to 81 degrees without any assistance from a heater.  Have you verified that the heater really is off by grabbing it?

[four_by_ken]

Is the tank located by any heat vents? A canister filter just doesn't typically use enough power to raise 125g of tank water to 81 degrees without any assistance from a heater.  Have you verified that the heater really is off by grabbing it?

I was going to say the same thing.  Unplug the heater.  Only way to tell for sure its 100% off.

A heater vent also should not warm the water that much.

[Marty]

Beyond what has already been mentioned, what type of lights are you using?

[olliesshop]

On the filter, it feels warm to me, similar to the water temperature.  Should be cool?  I really need one of those infrared thermometers to tell for sure.

I unplugged the heater yesterday and didn't think to check if it was warm to the touch.  Before that, I switched heaters with another tank that was maintaining a lower temperature and that didn't help any.  Now it's time to wait some more ...

[olliesshop]

Beyond what has already been mentioned, what type of lights are you using?

I'm have four 39 watt T5 bulbs above the glass cover.  They definitely get hot, but I've had them since I got the tank.  Although, I just put in all new bulbs in January.  The timing is right ... could new bulbs be hotter than the old ones?

[cranialdisturbance]

What is the room temperature?

[olliesshop]

Also, on the vents, there is a heater vent right behind the filter.  So I just closed it, since it was pumping out hot air right at the filter.

[four_by_ken]

Actually... that vernt could be it!

With the temps as cold as them have been, I would guess your furnace is running a lot.

[olliesshop]

What is the room temperature?

Right now it's 70.0.  It normally runs about 70-71 degrees.

[Marty]

I doubt that's the sole reason.  If you had something like metal halides, that would be a significant source of heat. 

You could try leaving the lights off for a couple of days as part of a process of elimination.

[olliesshop]

Actually... that vernt could be it!

With the temps as cold as them have been, I would guess your furnace is running a lot.

I agree, it makes sense.  Although, during the summer, with the A/C blowing, the tank was running at 80.1 degrees ... hmmm

[olliesshop]

I doubt that's the sole reason.  If you had something like metal halides, that would be a significant source of heat. 

You could try leaving the lights off for a couple of days as part of a process of elimination.

Good idea.  I think I'll wait, though, to see if unplugging the heater and turning off the vent helps. 

BTW, I really appreciate all the responses.  This really has helped!

[Super Turtleman]

How's this going?