Digital or Glass thermometers?

Which is best and more accurate and which would you prefer using in your own tank?

 

Ive always found glass to be more accurate

 

My take:

Digital strip thermometers

These are not very accurate and should be avoided. They have a sticky side that is pasted to the outside of the aquarium. This means that the glass temps are measured and not the actual water temp. Although these may be similar I prefer a more precise measurement. With time these also tend to start pealing off making there reading even more inaccurate.

Digital thermometers with probes

These usually have a display outside the aquarium with a long wire with a temp probe at the end that is inside the tank water. They are said to be 0.5 degrees off +- which is good enough I guess. I just find they look better in the package than what they do in use. I never know what to do with that long wire. I am also not sure on the quality of the probes used. If you go this route, I would go for something of lab standard or similiar(garanteed analysis on acuracy and calibration) Most of the alcheapos I have used fall victim to water spilling on the display making them as good as a paper weight.

Glass thermometers

These sit inside the tank. Most of them use an alcohol based liquid stored in a little bulb at the bottom, when the temp rises the alcohol expands thus rising up the tube offering you a temperature reading. IMO these are the most reliable and most practicle. I avoid the cheap chinese ones. I use this one which retails for about R70.00 last time I checked. The big draw back with these is the fact that they are damaged easily. One small bump in a water change and they could be toast. For this reason I remove mine every water change and give it a good cleaning to remove all excess algae ect. Another glass therm serial killer would be your trusty magnet cleaner... Be careful.

 

Thanks Verndog, most helpful. Appreciate the feedback. I had my daubts about the stickon thermometers.

 

If you take a box full of glass thermometers and compare them you will find that they vary from each other up to 2-3C. This is because the little strip with the temperature reading on it does not always sit at exactly the same place. I normally look at a group of them and choose the ones which give the same reading as the majority of them.

If you look at outside digital thermometers with the wire and probe inside the tank they too differ from each other, normally by a smaller margin. I do not even look at the stick-on strip thermometers. There are also wireless submersible thermometers available. I have not tested them, but I would guess that they would be more or less the same. The only drawback with them is that their reading is normally only to the nearest degree and not part of a degree like the wired one.

Since I know thermometers are not that accurate I rather use it as an indication than an exact number. If I for instance want to keep my tank at 26C, one degree either way will not be detrimental to my fish as long as it stays more or less constant and you do not keep your fish at extremes (very hot/cold).

 

Hi @AquaS, I take it as a rule of thumb as well and keep my tanks at 26 just in case its a degree higher or lower then the indicated thermometer temperature. Thanks for the feedback very informative.

What would you guys suggest: Glass or Digital?

 

digital if you clumsy and glass if you not LOL...:top:

 

@Lloydster. LOL those were my thoughts, as I'm pretty clumsy.

 

I'd go glass any day of the week. I have had 2 of those silly digital ones in the same tank, and the temp difference was 5 degrees... So, Glass all the way.

 

I prefer digital as long as I know it is as close to correct as possible. It is a lot easier to read. I used double sided tape to stick mine to the wall, so when I enter the room I can immediately see if the temp is still fine from a distance. With the glass ones you have to be close to the tank to read it and if the sucker stop sticking to the glass you have to open the top and take it out to read.

I also find many customers, especially the older folk, have problems with reading the fine lines on the glass thermometer. So every time they want to check the temperature they first have to go find their reading glasses. So I suppose it depends on your personal circumstances as well.

 

I have a glass one on one side of my tank near the outflow into sump which is currently reading in-between 24-25 degrees. On the other side of the tank, the inflow, the in tank digital is reading solid 25. So it think both.

The in tank digital one I have gives me temps to a point of a degree. The problem I have had with them in the past is that within time, the seal goes, water gets into the battery compartment and then it's gone to hell

 

Lol, that's why I don't like using the alcheapo ones. The sera precision readings are printed outside the glass tube. Not much room for error there.


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I tried the glass route, besides being difficult to read my Oscar thought it was funny to try eat it, landed up in pieces.

I now use submersible digital ones that I have found to be accurate when testing using the temp probe on my multimeter that I trust.

This is what they look like and are found at most LFS ranging from R50 to R80. They come with a spare battery and if you do preventitive maintenance you can change the o-ring at the back so that it doesn't perish and ruin your thermometer. You just stick it on the inside of the glass where ever you want, quick and easy to read with point readings.

 

i have digital in the 60l and glass in the 14l nano. Prefer the glass, for me it's more accurate but as @Verndog better to remove with water change, coz I already cracked my glass before.

 

glass for sure and they are usually cheaper than the digital ones

 

And far more accurate.


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Glass.

I tend to look at it this way. Anything that I "can avoid" that uses power I won't use. Too much hassle in maintenace and then there's the trust issue. I can buy 8 glass Thermometers for the price of one digital. 8 thermometers would last me more than 10 years. Any battery powered unit that can do this?

Sure if you have one and trust it, good on you. I just don't see the point. Having an item 10 times cheaper doing exactly the same thing makes more sense in my opinion.

But that's just my opinion.
Cheers