Reef tank getting hotter and I don't know why. Help?

[Perpetual Novice]

I have a 30-gallon biocube. The hood has been removed and replaced with a custom acrylic panel that sits on top and a China Box light that is hung above it. There are two nano skimmers in the back section in compartments 1 and 2. There is a 20-watt analog heater in the third chamber with the stock return pump. Finally, there is one of those tiny, cheap, off-brand powerheads that comes with a flow pattern controller. That lists all the sources of heat I can think of in my tank.

Usually, the tank stays at 80-80.3 degrees F. Right now, and for the past couple of days, it has been at 83! I use a cheap digital thermometer to read the temperature. They're not accurate, I know, but I have 4 others lying around which all read within +- 0.4 degrees of each other and confirm the same results.

The tank normally runs at 80 because the light really seems to heat it up and that's the temp it reaches with how fast the tank is able to dissipate heat. The heater only, if ever, kicks in at night and is set to 80. I'm ok with 80 and have adapted my coral stocking choices to match it (mostly SPS). I'm not worried about the fish at 80 because the skimmers add so much oxygen.

But 83 is not ok! and I don't know why it's happening. I can confirm that the heater is not malfunctioning and never comes on. I have dimmed the light to add less heat. The thermometer probe is in a good location for reliable readings. My apartment was at the same temperature it always is, but I've just started keeping the air even cooler the last few days with negligible impact.

The only things I have changed in the week are tweaking the flow settings on the powerhead and moving the heater out of the main tank section and into the filter compartment.

Any ideas why this is happening or how I should go about troubleshooting??? I wouldn't say this is an emergency ... yet. My corals are annoyed but not suicidal at the moment.

 

[C. Eymann]

Tweaking the flow settings? sending more power to the pumps? power=heat? shorter pulse modes possibly making pumps run hotter?

That's the only variable you listed that sticks out to me.

 

[S2G]

You said you put an acrylic panel on top. So basically you sealed it like a box. It sounds like your lights are heating it like a greenhouse. Unless im misundetstanding

 

[Silver14SS]

You could try unplugging items one by one to see which one is adding the heat, or try something like a Kill A Watt meter to see if you can pinpoint if one is using more energy than expected.

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House temperature change at all?

 

[c.poindexter]

Cooling is helped by evaporation of the tank water. With the lids it is not evaporating as much, I would say remove the lid and see where that gets you. You could also just verify that the heater is not running more than it should and the pump is not giving off excess heat.

 

[SlipperyWhipple]

Remove the lid, get a screen if you need something to prevent the fish from jumping out, raise the lights, and increase surface agitation. If temp doesn’t go down, put a small fan blowing across the surface. Also, take your heater out of the equation because it could be malfunctioning.

 

[sarcophytonIndy]

I would unplug the heater first, and see if that makes the difference.

 

[Perpetual Novice]

The back section of the tank where the filter is does not have a lid so evaporation occurs there

 

[Seanislav]

Get airflow over the top of the tank. The lights are heating everything topside, and the acrylic panel you mentioned is trapping heat inside, which transfers to the water. A screen over the top of the tank instead of a solid panel should help to dissipate the extra heat.

 

[Perpetual Novice]

One of my skimmers just stopped working. completely not running. Im wondering if some components were malfunctioning and generating excess friction?

 

[ZoWhat]

I believe most consumer grade thermometers are rated to be +/- 1°C

 

[Perpetual Novice]

I believe most consumer grade thermometers are rated to be +/- 1°C

yes. that's why i bought 4 and took the average.

 

[C. Eymann]

One of my skimmers just stopped working. completely not running. Im wondering if some components were malfunctioning and generating excess friction?

Absolutely a jammed impeller will make a pump run hotter.

 

[stanleo]

My tank did something similar after I added a refugium and another light source for that and the pump for it. I found that my heater was coming on when it shouldn't so I put it on a timer to only come on at night during a five hour window until I was able to find an affordable external temp controller. After two days I have yet to see the controller turn the heater on and I haven't had any temp spikes but during the day the temp does go up a degree because of the lights for the DT and the fuge. I too have a lid on my display with no lids on the sump or fuge. Having a light shine through a glass or acrylic lid will create a greenhouse effect and raise the temp. The evaporation from the sump is helping but not really that much.

I would look at moving the heater from the sump back into the display. I would also lower your desired temp to 78 or 79 that way if you still continue to have temp spikes its more like 80 or 81 and not 83 (I would freak out!) Also, look at a temp controller. There are inexpensive options. I found one for 35 bucks that was super easy and seems to work really well.

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