# How accurate are the cheap floating in-tank thermometers?



## KhuliLoachFan (Mar 8, 2008)

I'm not talking about the electronic or any fancy kind, but the kind that would have, many years ago had a drop of mercury at the bottom, and these days it's some other red chemical, and then a little vertically printed scale. There's a suction cup on the thermometer, and I usually submerse it about 1" below water surface.

In my unheated goldfish tank (for my son) seems to be at 78F, even after the lights have been off. My air temperature in the apartment is between 64 and 70. Could my filter be heating the water, even when the lights are off? Or is my thermometer a piece of crap? I wanted my goldfish tank between 68F and 70F and it's almost 80! Am I hurting our goldfish?

W


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## Calmer (Mar 9, 2008)

Test the thermometer against another one and if you only have that one then buy another thermometer. If you need to buy one then look at all of them in the store and take the average reading one. I have one for every tank and I make a point of checking them every day along with my co2 pressure gauge. The pump motor will not heat up the water at all from my experience with HOB's. It seems your thermometer is not quite right.


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## ameekplec. (May 1, 2008)

Pretty good. You can get a mercury thermometer (I have several from a photo lab chem set) and test them. I have found the alcohol ones (red) to be pretty good, being about the same as the mercury thermometers.


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## Ciddian (Mar 15, 2006)

i've had very good luck with them too. I have messed mine up before as well LOL but i always had a few kicking around to check it.


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## KhuliLoachFan (Mar 8, 2008)

We have calibrated temperature sensors (NIST traceable), accurate to 0.001 C at work. I'm going to borrow one tomorrow night. I bought two more $2 thermometers at BAs today, and they both read the same. So either I have four thermometers with about an +8.0 F bias, or something is heating this goldfish tank. It's a fluorescent fixture, the usual cheap black plastic hood and lights, no heater (obviously) and a HOB AQUEON '29g' rated filter on a 10g tank. My next step is to take the AQUEON off and put an AC50 on to see if the pump motor (which is potted and has water flowing over the potted motor, thus being somewhat water cooled on this model) is significantly heating the goldfish tank. The aquaclear AC50 hob pump design is different than the AQUEON. 

W


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## sawman88 (Sep 29, 2008)

i find it highly unliely that a HOB filter could heat the water that much. as they use practly no power at all. its a freak chance that you aquarium could be near a hot spot? maybe a draft of hot outside air comming in. but it could be the light as well get a chiller


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## planter (Jun 9, 2008)

There the only ones I use. Best peice of equipment you can buy for the money. 

They are better then those stupid black strip ones that glue to the outside of the tank

for example the one I'm staring at right now reads like this 

78 D - yellow
80 D - blue
82 D - brown

What the hell does that mean anyway?


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## KhuliLoachFan (Mar 8, 2008)

The tank is in my apartment, well away from the radiators (steam heated radiators). There are no sane temperature controls (thermostat) in any of the apartments in my building. And yet the red (alcohol) thermometer when left in the room air for ten minutes reads ten degrees lower than in the tank. I am leaving the lights off for a full 24 hours to see if the fluoresecent ballast is heating the tank at all. 

I think the previous poster was joking, but anyways, I'm certainly NOT going to buy a chiller for my goldfish tank. Nor a summer home in Antartica.

W


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## Darkblade48 (Jan 28, 2008)

KhuliLoachFan said:


> I am leaving the lights off for a full 24 hours to see if the fluoresecent ballast is heating the tank at all.
> 
> W


I think you may find that the ballast/lights are indeed causing the increase in temperature. You'd be surprised at how much lights can contribute to increasing temperature.

Also, keep in mind that the little piece of paper/cardboard inside the float thermometers might shift a little, causing erroneous readings (though this isn't your case, it's worth mentioning).


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## conix67 (Jul 27, 2008)

I'm sure the aquaueon filter is contributing to the heat generation, since the motor is submereged in the tank water all the time. I have one but never used in unheated tank.

I prefer glass thermometers over the digital stick on ones.


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## ameekplec. (May 1, 2008)

You would be surprised how much a single submerged motor can raise the temperature of the tank by. But it does operate 24/7, so it's constantly radiating heat.

Also, try to check your temps an hour before, after and during lights on, to see if there is a fluctuation (since three's no heater). If there is, then it is most likely your lights contributing to the heating. BTW, is it a closed top or open top tank? If eat is an issue, you might want to consider keeping it open top or having a mesh top for the tank.


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## KhuliLoachFan (Mar 8, 2008)

Lights made no difference, so I'm putting the Aquaclear 50 on beside the other filter, going to run them together for 24 hours and then pull the old filter out, and just stick the media from the old filter floating in the tank. I've had the AC50 sponge juicing up in that tank for two weeks, so I hope not to cause a new 'cycle'. I'm totally impressed by the heating capability of the Aqueon pump motor. 

W


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## Cory_Dad (Apr 18, 2008)

On my 10 gallon I have AC20 and AC30 with single strip fluorescent, room temp is 23.5, tank reads 24.5.


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## KhuliLoachFan (Mar 8, 2008)

After 48 hours without lights, the room temp was still 8F above room temp. I hooked up the AC50 tonight and I'm going to run it for 24 hours then pull aqueon out and use it on another tank.

W


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## Cory_Dad (Apr 18, 2008)

Why don't you just take the thermometer out of the tank and lay it beside your room thermometer? See if they match after 1/2 hour (dry it off first).


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## KhuliLoachFan (Mar 8, 2008)

Sorry I wasn't clearer! I used the same thermometer to measure room temperature as the tank temperature, then another, then another. Which means, for sure for sure, the tank is 8F hotter, even if the scale is offset a bit, it can't be moving up and down for no reason. It makes perfect sense now because Aqueon pump motors function emersed in tank water, whereas the Aquaclear motors are outboard (below and outside tank itself) and thus are air cooled, and do not heat the tank water. 

W


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## Cory_Dad (Apr 18, 2008)

KhuliLoachFan said:


> Sorry I wasn't clearer! I used the same thermometer to measure room temperature as the tank temperature, then another, then another. Which means, for sure for sure, the tank is 8F hotter, even if the scale is offset a bit, it can't be moving up and down for no reason. It makes perfect sense now because Aqueon pump motors function emersed in tank water, whereas the Aquaclear motors are outboard (below and outside tank itself) and thus are air cooled, and do not heat the tank water.
> 
> W


Doh! <slaps forehead>

Thanks for clearing that up. I kept thinking to myself "Isn't the answer obvious?". It was, but to a different question.

Cheers.


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## KhuliLoachFan (Mar 8, 2008)

I did some research and those "filter-in-hood" eclipse all in one systems also heat the tank up so much that goldfish aficionados report the tanks are unsuitable for goldfish use.

W


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## KhuliLoachFan (Mar 8, 2008)

And now that I have figured out my thermometer issues, I've realized that when the heaters kick on in my apartment building, the room temperature is a balmy 75 degrees F now. There's no hope for keeping a goldfish at 68F in my building, as there are no thermostats in the units. I guess I could leave a window open, but that seems kind of evil.

I wonder how long a black moor goldfish can survive at 75F+.

W


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## Shattered (Feb 13, 2008)

You could always get the "chiller" unit, that was mentioned. Haha

Good to hear that you found your culprit.


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## duffgrot (Jul 4, 2008)

Your Black Moor should have no problem living at 75 degrees, as long as the temperature change is a gradual one. It is not the ideal temperature for a goldfish and will add slight stress, but as long as you keep the water quality pristine, he should have a great chance. Some things you might look into to keep the temperature down:

1. Are you adding conditioning salt? Salt water heats up faster than pure water, therefore it cools slower. Make sure you aren't using salt as a preventative measure and only if you encounter ich.

2. Have you thought about removing your hood? Without a hood your tank would experience much more water loss due to evaporation. The evaporation would definately cool your tank down quicker, just as when we sweat it cools us down. I would not worry about keeping your goldfish in the tank, as they are traditionally not jumpers, especially those of the fancy variety, with the short, squat body type, who could not develop enough speed to do so.


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## Cory_Dad (Apr 18, 2008)

Good call [edit] on taking to hood off duffgrot.

Along with that idea you may also want to look at your water agitation for both increasing DO and to accelerate evaporation. A big air stone should do it if it creates a lot of bubble on the surface that will pop and create tiny droplets. Of course, don't put it near the glass or else you'll get a very quick calcium buildup on the tank rim.

But you're really fighting a losing battle here. If the room temp shoots up to and over 75F then your tank will slowly follow. And also as duffgrot mentioned, quick temperature fluctuations will stress the fish even more.

Try the hood less tank and see how it works. If it doesn't help then place the tank near a window, open the window a crack and make sure you have a good heater for those cold nights.

You'd think with this energy crisis we're having, apartment owners would jump at the opportunity to allow residents to control their apartment's temperature, at least allow them to lower it.

Good luck and cheers.


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## sawman88 (Sep 29, 2008)

stick the aquarium in your fridge and then use a heater to keep it at your optimum temp


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## Cory_Dad (Apr 18, 2008)

sawman88 said:


> stick the aquarium in your fridge and then use a heater to keep it at your optimum temp


Doh! <slaps forehead> Of course, it's so obvious.


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## ameekplec. (May 1, 2008)

If you're serious about keeping the temps down and are willing to make an investment, look into a chiller. Reef tank owners use them as the metal halide lights they use can heat up the water, and a few degrees matters when it comes to sensitive corals. Just look up chiller and you should get a bunch of options. 

Generally, the smallest chiller I have seen online (ice probe chiller) runs you about $250, and the larger chillers, obviously more but again, it depends on how serious you are.


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## KhuliLoachFan (Mar 8, 2008)

For my son's $5 goldfish in a 10g tank, even $250 chillers are not an option. 

If this goldfish perishes, we're not buying another one until I move into a house.

There's no way we can take him back to the store or give him away. He's my son's goldfish, and he would cry just as much if we take him back, as if he dies. I just hope the lil' guy doesn't mind it. So far he seems fine.

W


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