So I bought an ATC-300 heater controller on eBay over the weekend because I'm not confident in my heater's ability to keep the tank temperature regulated and it arrived today.

I plugged it in tonight to find out that it only displays in degrees celsius, which isn't my native unit of measure for temperature. Okay, no big, I can get past that.

Next I compared the temperature on the ATC to the temp on my digital thermometer on the tank and found about a 4 degree difference (a little over 6 degrees fahrenheit) between the two measured values, with the ATC registering the higher temp. Of course, this caused me great concern, so I ran out to one of the big box pet stores and got one of the old fashioned "mercury" style thermometers that stick to the side of the tank.

The new thermometer agreed with the ATC. Argh, That means I've been keeping my tank between 85 and 86 degrees (F).

To fix this, I'm going to use the ATC to slowly lower my tank temperature back to the 78-79 range over the next several days.

I wonder if this is why my clown fish hasn't been eating lately. I've been trying frozen mysis shrimp, some "Joes Food" I picked up at MAX, and even some marine flake food. The fish swims up to the food, "sniffs" it, then moves on.

So, moral of the story, always have a backup thermometer and check the readings once in a while to make sure there hasn't been any drift in the readings.

-Chris

Thanks for this reminder.

What brand of controller did you buy? The Ranco I have now and my old Aquanetics both switched from C to F in the set menu.

Try soaking your clown's food in garlic. It is a good appetite stimulant and all around tonic for your fish. I use it every time I feed no matter the type of food.

I ran into this also a couple weeks ago I didnt think much of it till I saw your post I have three diffrent temp on three tanks that are all hooked together I think I will go get some mercury thermometers and see which is right now Thanks

Do be careful, most "mercury" thermometers are not mercury and cheap ones may be inaccurate as well. BTW, my $10 Coralife digital is within a degree of my $100 controller.

i run 2 coralife digitals ... 1 on my DT and one in my fuge. they are always within 1 degree of each other so i usually go to the middle of the road. i love those litlte black boxes !!

I agree. I love those digital thermometers. I have heard people curse them because they don't match what their heaters are reading, perhaps it is the heater that is "off". I have a couple of them and they are always right in line with each other and the"mercury" type styles, which in most cases are hard to see/read perfectly.
One other piece of advice, don't try and use a digital "childs" thermometer it only goes down to 90 degrees.

The one that was giving me the crazy readings was actually a Coralife. Here's a link to one: Aquarium Water Temperature: Coralife Digital Thermometer (http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3744+12089&pcatid=12089)

When I bought the glass thermometer, I got that one because the only other ones that were at the big box pet store that was open late that night was the same Coralife, and I didn't want to get the exact same thing I already had.

The glass one agreed almost exactly with the new controller and once I got two of the three to agree, I figured I'd gotten the actual temp of the tank.

CarmieJo had asked earlier which controller I got and it's an "ATC-300". Here's the link to an eBay auction of the same thing: ATC-300 2 CHANNEL AQAURIUM TEMPERATURE CONTROLLER REEF - eBay (item 150235208257 end time Apr-15-08 08:08:55 PDT) (http://cgi.ebay.com/ATC-300-2-CHANNEL-AQAURIUM-TEMPERATURE-CONTROLLER-REEF_W0QQitemZ150235208257QQihZ005QQcategoryZ11743 5QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)

Bottom line, I guess, is to have two measurements to ensure that you're not cooking your fish. My zoas have started to color up nicely now that the temperature's down to a more reasonable state.

Another lesson learned -- the hard way. :)

Multiple devices are always good. Multiple devices in agreement are even better!