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That's no good! I have that same digital thermometer, I hope mine's not going to break. I've had mine probably 6 months.
 

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Discussion Starter · #3 ·
Well, it's unfair to say it's broke. Actually the room temperature still works, just the one in the tank broke. :(
 

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Honestly, after trying several digital thermometers, the best one I have found is the old fashioned, suction to the glass, red liquid, glass encased kinds.

I gave up on digital ones when I tested 7 of them all at once, and no two would give me the same reading (some were off by over 8° from each other!). Some simply did not work, others got stuck at certain temps, some would "rise and fall" over and over again, and in the end, I couldn't figure out which one(s) were accurate enough to actually use. I tossed them all.

I also discovered that digital thermometers are slower to respond to temperature changes which I found frustrating during water changes.

If you get another digital thermometer, check its rated accuracy. Some are as much as ±2° which is a large range. For example, if the thermometer reads 78°, is that the actual water temp, or is the temp reading +2 (water is actually 76°) or -2 (water is actually 80°). From 76° - 80° is a big difference.
 

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Discussion Starter · #5 ·
Oh. That is sad.

I have read about the Ranco themocontroller which are suppose to be very accurate. If I just plug the heater into it and set the Ranco, folks say the temp will stay within 1 deg. I think it has a digital display of the currrent temp. Is that a better way to go?
 

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"Tom Aquarium Temperature Alert" gives the same reading as glass thermometer. But it displays only in Fahrenheit. I got mine a long time ago and it continues to work.

http://www.petsmart.com/product/index.jsp?productId=2755306
It's not accurate though. I found it gave me very different readings than my Lifegard Big Digital Thermometer. I finally ordered an Accu-Safe thermometer from Avogodro's Lab Supply on Ebay, which has been calibrated and verified to be accurate within one scale division. I use that when I want to REALLY know what the temperature is, all the other thermometers are off. Tom's Aquarium Temp Alert was off by 4 degrees. Find an accurate glass thermometer and check your digital thermometer, good chance it will be off.
 

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Well, mine and the VWR one are calibrated and tested against standards traceable to the National Institute of Standards and Technology and were found to be accurate to within +/- one scale division for temps below 230 F. It comes with a certificate and a serial number, from there I take their word at it.
 

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To establish the accuracy of the glass thermometer, I checked it against the reading of the room temperature thermometer. They both gave the same reading.

Then I dipped the glass thermometer into tank water and placed it alongside the probe of Tom Aquarium Temperature Alert. They both gave the same reading. To me, that means the Tom Aquarium Temperature Alert is very accurate.
 
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