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Thermometers: What The Heck!


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Do you trust your thermometer?  I don't!  I suspected something was off when I setup my quarantine tank (5 gal.) with a new heater and a floating thermometer and nothing was even close to lining up temp. wise.  I set the heater for 78 degrees and the thermometer registered 84 degrees!  What the heck!  The heater manufacturer claims an accuracy of +- 2deg.  so I had 3 old glass floaters left in a box from back in the day and I dropped them in the tank too.  So now I was getting readings from 70-84 across 4 different floaters!  Nothing was matching up!  I had purchased one of those fancy stick on black digital thingies (I hate those things, you gotta use a flashlight to see them) and stuck that on too.  That one actually agreed with the heater!  Go figure!  I've ordered a new floater here from the Co-op and hope it's a good one.  So I guess the point here is do you trust your thermometer?  How do you verify the temp?  It goes without saying how important this is.  Any suggestions or recommendations?  Temp gun?  I'm just getting back into the hobby and I don't want to start out by cooking anything.  Thanks for any help.

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On 8/15/2021 at 2:15 PM, Brymac1 said:

I use an Inkbird heater controller that has two temperature probes to make sure my tank is at the right temperature. It will also shut off the heaters if they get stuck on.

I use these in all my tanks. I use the non WiFi single probe dual plug ones they are cheap and reliable. I don’t trust therm or heater dial. I calibrate the inkbird to a temp laser gun. They are super simple to operate and calibrate.  I had to many heaters poach fish as you said in your intro…ahh the good old days….not 🤣

Edited by Guppysnail
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On 8/15/2021 at 1:56 PM, quikv6 said:

To be honest, I trust a thermometer more than I do the heater dial. I've had multiple heaters of the same style that were off quite a bit.

I use the black digital thermometer AND a glass one. It's good to have checks and balances.

Definitely.  I've never owned one that was exact.  Usually I have to keep them a couple of degrees lower. 

I have a IR thermometer I use, and I have a couple of digitals in a few tanks.   

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You can get a NIST traceable thermometer that accurate to +/- 0.1 F and use it to calibrate your other thermometers. Here is the one I use:

300032080_pHcontrols.jpg.3dc9791ec8528b2

Once the thermometers are calibrated they hold calibration pretty well. Here are 3 calibrated temperature probes all in the same buffer solution at the same time giving close to the same reading:

image.png.3e068ac16570c39cd2abc6efe67463

But the thermometer I use most often is my hand. If the water luke/cool it is low 70s F. If the water is lukewarm, it is middle 70s F, is the water is warmish it is about 80 and if the water is warm it is upper 80s.

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I bought about a dozen of the glass floating thermometers, then lined them all up in the middle of a large tank. Several had the same temp, which was near the middle of the other temps. I took them out and put them in separate tanks, with a post-it note on the black rim by it that said "within 1 degree."

The others got put in labeled ziplocs to use if needed. The labels are things like "real temp is below this thermometer." 

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I calibrate against a 15$ catheter thermistor.  Since it's a medical device it is very accurate near body temperature but you need a multimeter and a lookup take to use it.  Turns out my digital meat thermometer happens to be spot on.

 

A LOT of ice with distilled water will also be very very close to 0 C as that's an intrinsic temperature standard.  But I have thermometers that read spot on at 0 but are pretty off at tank temps.  I assume they get factory calibrated with ice water but don't have a calibration point near tank temperature

 

 

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I use a digital thermometer I picked up at a LFS that came with an extra battery, I used a digital meat thermometer to confirm accuracy, it was so accurate I bought three more, they're just as accurate, and I am so happy.

Those glass tube thermometers get jostled around so much in transportation that the pasteboard gauge gets jostled out of position, maybe by a little, maybe by a lot.

You should consider raising the temps in your tanks to about 85 degrees to prevent diseases.

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On 8/15/2021 at 6:23 PM, Stephanie I said:

I used the thermometer I have for making tea to check the tank temperature one day.

I use a tea thermometer when I’m doing water changes. It’s fast and seems accurate! Otherwise I use the floating ones. Which are hopefully accurate. Though I’ve never tested them…

@Daniel I wish I could judge it by feel but I’ve learned that for me, how the water feels depends a LOT on the temp in the house and how exothermic I am. The same temp water can feel really cold in the summer but nice and warm in the winter.

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On 8/15/2021 at 7:43 PM, Hobbit said:

I use a tea thermometer when I’m doing water changes. It’s fast and seems accurate! Otherwise I use the floating ones. Which are hopefully accurate. Though I’ve never tested them…

@Daniel

I don't think I've ever actually calibrated the thermometer I use for making tea.  Although it can't be too far off because my tea tastes good after brewing (most of the time). 😃

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I always compare a new therm to at least one old one that I trust, no matter what type. Plus I check with a hand against the glass or in the water depending on what’s going on that day.

Like @Daniel I know that slightly cool is low 70’s for shrimp, plant, and blackworm culture tanks, neutral/lukewarm to touch for my community and puffer tanks at mid-ish 70’s, and slightly warm for Betta tank at high 70’s to 80.

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On 8/15/2021 at 4:05 PM, Streetwise said:

@CalmedByFish, have you tested an Apex thermometer or pH meter?

I don't even remember hearing about those until this thread... nor a tea thermometer. 

On 8/15/2021 at 8:16 PM, Odd Duck said:

I check with a hand against the glass or in the water depending on what’s going on that day.

Like @Daniel I know that slightly cool is low 70’s for shrimp, plant, and blackworm culture tanks, neutral/lukewarm to touch for my community and puffer tanks at mid-ish 70’s, and slightly warm for Betta tank at high 70’s to 80.

I should learn this little trick! It seems so obvious, now that I hear it. I make a point of keeping adaptable species, so I don't really need perfection.

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On 8/15/2021 at 9:42 PM, Daniel said:

But the thermometer I use most often is my hand. If the water luke/cool it is low 70s F. If the water is lukewarm, it is middle 70s F, is the water is warmish it is about 80 and if the water is warm it is upper 80s.

It is the same principal as my Stone Weather Centre, very accurate and 100% reliable:

If the stone is wet ; It is raining.

If the stone is dry; It is not raining.

If the stone is white; It is icy or snowing.

If the stone has gone; there is Hurricane.

😉

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Haven't been able to post since my Xfinity has been down for the past 3 days due to the storms up here in MI.  Thanks for all the responses here.  I ordered the "ETEKCITY 774" from Amazon for $23 in the mean time and I'm really impressed with it.  It turns out that only one of the floaters and the digital sticky thing matches the temp gun.  So my two tanks are at 79.5 deg. and that's with the heaters NOT coming on.  I think a degree or two cooler would be better but we don't keep the air conditioning running all summer.  

Thanks everybody ...... I'm gonna go make some tea now    😉

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I have an Etekcity infrared thermometer that I use for everything. (The red laser dot makes a neat cat toy and can also be used to annoy the fish who think it's food and chase it around the tank.) I also have an instant read digital probe thermometer that's used for cooking and they both agree on temps. If you're shopping for a conventional glass tube type thermometer in stores, be sure to compare the readings on all of them. You'll find a general agreement on most with some varying wildly one direction or the other. Quality contorl for thermometers is not great.

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