# In search of an accurate thermometer



## Sacha (13 Apr 2015)

Hi folks, 

This is one of those things that has bothered me for my entire fishkeeping career. I have never been able to find an accurate in-tank thermometer. The best I have found is one built into the Seneye Home, but I don't use that in my tank anymore since it's a pain to have a computer attached to the tank and turned on 24/7. 

So, does anyone have a thermometer that they can trust and would recommend? 

I remember when I had a Juwel digital and a Superfish digital thermometer next to each other in the same tank. Juwel one was reading 27.5 while the Superfish read 24...


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## dw1305 (13 Apr 2015)

Hi all, 
Any old fashioned spirit based thermometers should be reasonably accurate. A lab. grade mercury filled one would be very accurate.

I haven't used one, but the UP "hang-on" glass thermometer should be fine for ~£6.

I never take any notice of the digital ones, they all become inaccurate over time. Usually I just put my hand against the tank glass. As long as it doesn't feel noticeably hot, or cold, things are OK.

cheers Darrel


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## Katch (13 Apr 2015)

I have an old lab grade mercury thermometer - it makes me nervous having it around. Mercury is very very nasty stuff when it gets out.

I'd go for a spirit based one - brewing supply websites should be able to sell you one. They're about 30cm long which makes the scale less fine than the titchy ones you get for aquatics.


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## Sacha (13 Apr 2015)

Thanks for the replies. Something like this? 
http://www.wilko.com/homebrew-accessories+equipment/wilko-thermometer-12-inch-spirit/invt/0022574


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## dw1305 (13 Apr 2015)

Hi all,





Sacha said:


> Something like this?


Yes that should be fine.

You might find that some of the aquarium ones only read from 10 - 40oC, which would nean that a shorter length thermometer may have simular sized scales.

cheers Darrel


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## ian_m (13 Apr 2015)

After going through 2 Juwel in tank digital thermometers (first one digit segments stopped, 2nd one leaked) and a Maplin one (started reading wildly wrong ie 38C !!!) I now have this.

http://www.jbl.de/en/aquatics-freshwater-products/detail/2495/jbl-aquathermometer-premium

Needs no batteries, doesn't leak, works 100% of the time for last two years and cost only £5. Occasionally falls off, but wipe glass, wipe sucker and stick back, or if can't be bothered, leave stuck in substrate works just as well.


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## sciencefiction (13 Apr 2015)

I used to have a Juwel one, it was off by 2-3 degrees, not worth the money.

I've had this one below for years. It's always been showing the same temperature as my TDS pen to the smallest digit, quite accurate. It needs to be outside the tank though, just the probe is in.

http://www.amazon.co.uk/Aquarium-th...sr=8-16&keywords=digital+aquarium+thermometer


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## Iain Sutherland (13 Apr 2015)

if its open top i love these and just £7
http://www.aquariumplantfood.co.uk/...thermometers/gush-glass-thermometer-10mm.html


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## roadmaster (13 Apr 2015)

I use cheap thermometer's sold at near any fish store.(suction cup type)
Have compared these with reading's from another when I thought/wondered if they were still working.
Many times, only two or three degree difference.
Not enough for me or fishes to be concerned with.


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## limz_777 (13 Apr 2015)

none in the aquarium market is good , science lab grade as mentioned or you can look into coffee thermometer


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