Looking For Best Aquarium Thermometer Recommendations

[Ch4rlie]

As the topic title suggests, I am looking for a good quality thermeometer thats pretty accurate.
 
At the moment, i have 3 different thermometers on my 3 tanks, a cheap digital LCD, floating glass and a digital stick on tank glass one and even have on fluval heater with a built in thermometer.
 
All three displays differing temperatures no matter which tank i swap them on to try and get an idea which is most accurate or reliable, none of them are i reckon as they are off by as much as +2/-2 degrees.
 
So its hard to know which is best to use, or even if all are rubbish!
 
This is fairly critical for me as I want an accurate thermometer as possible, as some of my tank species requires pretty exact temps, for example in one tank I have some asian rummynoses and they require temps from 18C up to 22C and in the same tank I have emerald danios which are from 20 to 23C and also have black cherry shrimps, so therefore I want water temp on that particular tank to be pretty much spot on at 22C, +0.5/0.5-.
 
I know am being particularly picky, but thats me!
 
Have had a look online, there seems to be conflicting information and/or poor testing results etc
 
So if anyone knows of or heard of a pretty decent thermometer at not too high a price, please let us know

 
Maybe even if you know how to calibrate certain thermometers, that would be good information as well.
 

 

[cooledwhip]

I know it's not an aquarium thermometer, but my cousin gave me a laser temperature sensor for christmas. He got it on amazon for like $14 bucks. It works great surprisingly, it gives me the temperature to the half of a degree. Plus you only buy one, and just go up to your aquarium water and click it, bam. instant temperature reading. It's instantaneous too, no waiting.
 
I can check the temp on the three tanks in my upstairs room in about 10 seconds max. The only delay is walking from room to room. 

 

[DWC]

Do you think they are "off" always, like thermometer A being always +2 what thermometer B is reading, or do you think they vary from true by variable amounts? If the former then I think just knowing the margin, say +2C, would allow you to adjust your "target" to account for the margin. If the latter and they can be +/- from true then you need another thermometer that is at least consistently off. I just ordered 5 new digital thermometers from Amazon ($2ea) and after installing batteries I left them all at room temperature and then all in the same tank, sensors near each other. Four were always identical in their readings and one was always 6F less. I am not going to use the latter, but could, allowing for the 6F fudge factor. Whether any are the true temperature, I guess I don't know, but my bettas are happy with a reading of 78-82F that the majority, now each in its own tank, read. Have you tried your three thermometers on the same tank at the same location and time? The laser sensor noted by John could give you the exact temp to compare your's to.

 

[Fishmanic]

I have this stick on one on two of my tanks and it matches perfectly to my floating/suction cup one.   Just today I checked it with an accurate instant read digital oven thermometer and all temps coincide exactly at 77 degrees.
 
stick on thermometer (great reviews on amazon)...best to use on glass aquariums ...I heard on  plexiglass tanks it may not read as accurate
https/www.amazon.com/American-Thermal-Aquarium-Thermometer-Vertical/dp/B000O3BEDK/ref=sr_1_4?ie=UTF8&qid=1466275281&sr=8-4&keywords=ati+aquarium+thermometer
 
floating or suction cup thermometer  
https/www.amazon.com/Marina-Floating-Thermometer-Suction-Cup/dp/B0002AQITK/ref=sr_1_1?ie=UTF8&qid=1466275538&sr=8-1&keywords=marina+floating+thermometer
 
quick read oven thermometer ( this is a very accurate thermometer)
https/www.amazon.com/Touchscreen-Thermometer-Thermometers-Countdown-Stainless/dp/B01A6PBAGQ/ref=sr_1_2?ie=UTF8&qid=1466275643&sr=8-2&keywords=digital+touch+screen+oven+thermometer
 
all three read exactly 77 degrees
 
I mainly rely on the stick on tank for fast read of tank temperature...works well for my tanks...the floating thermometer is difficult to read since it's so small...I just used the oven thermometer to see the accuracy of the other two and they are right on the button

 

[Ch4rlie]

Some good ideas there, giving me food for thought for sure.
 
Wonder if its worth putting all my thermometers into a large glass with ice, they SHOULD read zero, if any are out then may make a mental note its off by whatever reading it gives....
 
Then take it form there.
 
Also like the idea of the oven thermometer FM mentions, though can be pricey, certainly worth considering and use it every now and again just to check temps.

 

[coolie]

Try a lab thermometer - they are very accurate. They don't have that extra glass bubble around them like aquarium thermometers do which I guess is to stop it leaking into the tank if you break it? Or no? They only contain alcohol anyway, not mercury these days?

 

[Fishmanic]

the oven thermometer of course can be used for cooking and grilling....I use mine on the outdoor grill for steaks and in the oven for chicken...comes out perfectly to the temperature and doness you set it for.....it has a metal lined cord that is oven and grill proof...the one I listed is a touch screen model and is very accurate...it's only $20 shipped in the US...tested perfectly in boiling water which is 212 degrees F or 100 C

 

[eaglesaquarium]

Some good ideas there, giving me food for thought for sure.
 
Wonder if its worth putting all my thermometers into a large glass with ice, they SHOULD read zero, if any are out then may make a mental note its off by whatever reading it gives....
 
Then take it form there.
 
Also like the idea of the oven thermometer FM mentions, though can be pricey, certainly worth considering and use it every now and again just to check temps.

 
 
Ice WATER... need both the ice and the water... STIR AND STIR AND STIR...
 
For the best results, you will need to use CRUSHED ICE and some water mixed together and STIR STIR STIR.
 
 
 
 
BUT, this won't tell you anything about your target, in reality.  You'd need to get TWO readings of known values and calibrate your scale from there.  Also, most aquarium thermometers (alcohol ones) don't go all the way to zero on the Celsius scale.

 

[Ch4rlie]

So I guess a little bit of stirring is involved.....
 
 
 
 

 
 
 
 
yes, I did mean ice and water, crushed ice is a good idea though. Stir a little bit then leave for 10 mins then add the thermometers but unsure how long to leave thermometers for before taking a reading, 5 - 10 mins as a guess ? 

 

[eaglesaquarium]

We do this exact lab in my class.  Stirring is the key.  If you aren't stirring, you get the reading of a 'hot' or 'cold' spot, and not the average.  The goal is to have everything exactly the same temperature and the only way to do that is to stir.  The ice will likely start at a temp of about -10 degrees.  The water is more likely about 10-15 degrees (not sure on the exact temp in your area - in my area of the US, its about 50 degrees F).
 
So, the ice will need to 'warm up' and the water will need to 'cool down'... until they are both at zero.  Then the ice will begin to melt and while this is happening (and you stir) the temperature will remain zero degrees.
 
 
Two minutes or so should be plenty of time to wait.  To help speed the reading up to be more accurate, keep the thermometer in the fridge so that its closer to zero.  The less the thermometer itself has to change temperature, the more quickly the reading will be accurate to the water.  All of the parts need to be in thermal equilibrium with each other.

 

[StevenF]

It is important here to not confuse resolution and accuracy.  A meter that read down to 0.1C has a resolution of about 0.1C.  But the actual temperature may be 0.5C different so in this case the accuracy is not 0.1C.  Typically accuracy is listed at +/-X.XC number.  The Hanna temperature meter linked to below is about $40 and has a stated accuracy of +/-0.2C.  I suspect that is as accurate as you are going to get at $40.  Higher accuracy will cost more.  You can find meters less than $40 dollars but many are from china or Ebay and any accuracy rating you get may not be true.    
 
http/hannainst.com/products/testers/temperature/hi98509-checktemp-1-digital-thermometer.html.
 

 
 
This is fairly critical for me as I want an accurate thermometer as possible, as some of my tank species requires pretty exact temps, for example in one tank I have some asian rummynoses and they require temps from 18C up to 22C and in the same tank I have emerald danios which are from 20 to 23C and also have black cherry shrimps, so therefore I want water temp on that particular tank to be pretty much spot on at 22C, +0.5/0.5-.

Keep in mind the temperature recommendations for fish commonly are just guesses of what works well by breeders and researchers.  in many cases the fish in the wild often see some wild temperature swings and do just fine. I also highly doubt that temperatures in a stream during the hot dry season will stay below 25C in tropical and semitropical climates.  For example it is not unusual in the tropic to have several hot clear days in a row followed by a day of heavy rain.  So during the hot dry days the temperature of the water will increase each day, with some limited cooling at night, followed by more warming the next day.  While on the day of rain  all the warming from the 3 previous clear hot days  might be erased as the cool rain mixes with the warm water.  For salt water fish we have a much better idea as to the suitable temperature range because the size of the ocean give it considerable thermal inertial.