pamd

I went to all the chain stores around town yesterday to purchase a new thermometer. At least two batches of those so-called "floating" thermometers for $3 are inaccurate.

I pulled out about 10 thermometers from each store and compared them.

One batch was at Petsmart from their store brand, Top Fin. They were all in the same place, and they varied by about 4 degrees Fahrenheit from each other, right off the shelf, same room temp. Made in China. The second batch was from Petco, and looked exactly the same, although made in Taiwan, which also varied by about 4 degrees F. Interestingly, the pet store "fish experts" had never noticed this, and these are the thermometers they use in their aquariums.

I've done a bit of additional "scientific tests" on two new thermometers (ones I chose in the middle range) comparing to my old one, and they vary by at least 2 degrees F plus or minus.

I considered getting a digital thermometer, but I'd really not rather have yet another cord going in and out of the tank since the digital ones seem to not be waterproof and need the outside monitor plus probe.

Any recommendations?

Lucy

I don't have any recommendations, but your observations are really interesting. Thanks for sharing it.
I might test all the thermometers I have.

Regal

I've noticed the same thing. I have three in my tank right now. Two of them say 82 and one says 84. I have three different tanks and keep moving them and trying to compare the readings and the way the water feels to the touch.
I just bought another one a few days ago and saw the same thing, they are all slightly different in the store too.

COBettaCouple

I'm not sure if any are too accurate, but I find the strips (the removable ati ones) to be pretty good and next to digital probes, the best for our tanks.

pepetj

I go with the old classic glass thermometer that has the scale in the glass tube and attaches to the tank by a suction cup. So far cheap, safe, reliable.

Pepe
Santo Domingo

pamd

Pepe,

I suppose those are the same thermometers, but perhaps the ones you can get in Santo Domingo are closer in accuracy. Mine are the glass tube type with the scale inside on what appears to be a little piece of paper, and the most recent one specifies it uses alcohol, not mercury, for measurements. The others didn't specify. They all look the same, though.

Thanks, Pepe!

Edit: Moved to General Discussions, since there are not many replies where I originally posted in "Heaters." I can see why "Heaters" is a less-frequented part of Fishlore!

Tavel

Use the liquid crystal type (the "stickers") as a daily monitor. They're accurate within 1 degree because they rely on chemical reactions, not a calibrated scale (or "miscalibrated" scale in the case of the chinese junk thermometers, lol).

Then you can use a plain old kitchen thermometer or meat thermometer to get a more accurate reading if you want/need. but you'll probably find the sticker is right on the mark and won't bother with the kitchen thermometer after a while.

Do get the ATI brand though, very nice. They are only labeled even degrees (74, 76, 78, etc). Green means it's right on the indicated number, and orange means it's 1 degree below the indicated number. Super easy to read at a glance. They're accuracy is only limited by the fact they measure the surface temperature of the glass, not the water itself.

Fish Addict

To what Pamd, do they make thermometers with mercury anymore? Couldn't that be dangerous for you and your fish?

pamd

As far as I know, the measurements in the "tube-type" thermometers are made with alcohol, not mercury.