suction cup thermometer vs. outside stick on thermometer!

[Mr. Limpet]

It also has to do with what's around your tank. I have a vent near my DT and a stick on won't work because the ambient temp in the room fluctuates to much. As for the floating therm, I don't use the suction cup I keep mine floating at the opposite end of the tank where the heater is.

[Fishguy2727]

Honestly it amazes me that so many people still use those stick on pieces of junk and think they are as accurate as one that is in the water. It is pretty straight forward, the one touching the water will tell you the temp of the water, the one touching the glass and the air will tell you the temp of the glass and the air.

Use whatever you want, guess for all I care. But don't waste money on buying a new stick on.

[fort384]

...The glass is the temperature of the water

[Fishguy2727]

A photograph showing two thermometers with almost the same temp means that either one thermometer is off or that the air, water, and glass are all very close.

Water is very resistant (not conductive) to gaining or losing heat. This is why humidity plays such a massive role with weather (and why places like the desert can be so hot during the day and so cold at night while a rainforest stays relatively the same temperature).

It has been a while since I studied Physics, what exactly do the laws of thermal dynamics say that says that water will give up so much heat to glass better than air? Or that two thermometers, one in water and one on its container, will be as accurate?

After all this fluff and 'look what advanced topics I can bring up' are over, I still say don't waste your money on a tacky looking stick on thermometer from the 70s, there are better, more accurate options for about the same cost. My favorite cheapo thermometer is JW's Smart Temp Thermometer (white plastic with magnet mount). I think they should make it in black, but that is me. IMO if you you are going to use a stick on put it on the side of the tank towards the back wall (where I put any thermometer anyways).

I am amazed I care enough to write all this. If someone wants to use an ugly stick on from the 70s go ahead.

[allaboutfish]

i was just saying bc the suction cup ones are soo hard to read

[fort384]

Originally Posted by Fishguy2727

A photograph showing two thermometers with almost the same temp means that either one thermometer is off or that the air, water, and glass are all very close.

False.

I am not saying that the conductive properties of water are extremely high--in fact, compared to a material like say, aluminum, they are extremely low. I am saying that in comparison to air, they are extremely high. The thermal conductivity of water is about 25 times higher than that of air. Also, if you look at the heat transfer coefficient of water versus air, it can be on magnitude of 10 to 100 times higher for water, depending on the properties of the barrier separating them. It isn't a matter of "the laws of thermal dynamics" (although I suppose you could apply the 2d law). It is thermal dynamics in general.

We can agree on 1 thing: Stick on thermometers are ugly imo. You got me there. However, as to whether or not they work, they absolutely do. So, when it comes down to it, if someone likes the look of the stick on, and likes that they are easier to read, than they should use one, because accuracy is not a concern.