So the whole temperature dilemma in my tank has been driving me crazy and I don't know which reading to believe.

I have:

1. ADA Thermometer

2. Up Aqua Digital

3. Cheap thermometer

All give me different readings!

How can I go about getting an accurate reading, 100%, so that I can calibrate my Eheim Jager heater correctly? Should I need to calibrate my heater?

 

Are the readings vastly different?

1. Shows roughly 22.8

2. Shows roughly 25.5

3. Shows roughly in middle of #1 and #2

Heater calibrated to 24

That's a tough one. Are they all measuring roughly the same spot in the tank?

You can get differing temps in different spots, especially a bigger tank.

Since it's cooler weather, and heat is being lost all the time, I'm inclined to say the water temp is always going to be slightly under the temp set at the heater (assuming the thermostat in the heater isn't faulty). 

So it looks like the cheap thermometer is the most accurate (my opinion). In this situation I am putting more trust in the heater.

 

Heater calibration doesn't actually do anything.  Its far better practice to read the temp of the water (how else will you know if the heater is working or keeping up with losses?) and turn the heater up or down accordingly - the numbers on the heater knob are irrelevant apart from telling you which way to turn... and perhaps to give you a rough approximation of how far to turn it.

So I should start by putting the calibration back to factory and then measure?

They were all in the same spot in the tank, just don't know which one to believe.

I'll start over and see what they measure.

Important - a heater is not a thermometer.  Never believe the heater (they sometimes lie!).   

IMO you always need an independent measure of the water temp, even if its just a weekly whip around with a thermometer.

A heater is not designed to read the temperature of the water.  It is made to repond to the temperature of the water to turn a heating element on/off and other factors will be at play (heat losses, hysteresis, input voltage).  Subtle, but different.  The calibration of the heater will change slightly in tanks of different sizes and with the temperature of the room as these alter the duration of on-off cycles... we don't care about such small variations...but sometimes the thermostat breaks, or we forget to turn the heater on, or the element in the heater partially fails (could be hotter or colder).  The worst types of problems are normally the partial failures that we don't spot - e.g. heater is only putting out 70% of the heat it used to, cant keep up and all the fish catch a cold and die of white spot.

All that said - IMO give or take a degree or two rarely matters.  The real world varies a LOT more than our tanks,

 

Edit:  I would use 2-3 thermometers as you have done - chuck away any that are more than 2C out, and calibrate the heater to the remaining, but know that doing so is just for your benefit of seeing the knob on the heater have the same number - you still cant believe its going to be that temp all the time.

 

Edit... jeeze I crap on sometimes.

Edited September 1, 201510 yr by Grubs

Haha!

Thanks for the help Grubs.

Edit... jeeze I crap on sometimes.

LOL Grubs.

So what was your opinion to the original question?

1, 2, or 3 - which thermometer to believe?

Is there something, other than a cheap aquarium thermometer that will give me a more accurate reading?

I like to use analog thermometers, the type with the increments marked on the glass so they can't move. Preferably the type with a big scale so they're more accurate. When I buy them I have to go through a whole batch to find the ones that all read the same, ie right. I'll take those and leave behind the ones that are wrong - sometimes more than half the batch are reading high or low. Price doesn't seem to factor in. Once you have thermometers that you know to be correct, you can use them to calibrate others that might not be so good. 

If you don't have any that you know to be right, I you can't really trust any of them. I'd accept the middle value from the cheapo thermometer for now. What does the temperature display on your TDS pen show? 

Thanks for the reply kizshrimp. My TDS pen doesn't have temperature. I might go buy a few more different ones and see what they measure.

analog glass thermo is the best, but tbh out of 1,2 & 3 i will just go right in the middle of them and go with 3.

Out of curiosity, what heaters do you all use?

U are not alone 

U need to get temp with 0.1 celcius

there tds pen without the 0.1 celcius and it's really not recommended to use

dunno about fahrenheit

 

I can't emphasise my last point enough. Check all the thermometers in the shop when you buy and pick ones that all show the same temp, usually in the middle of the range. The quality control at the manufacturers is obviously useless. 

edit - when you're checking themometers to buy, don't put your hands on them, especially not near the bulb part. Not a good way to get accurate readings. 

@salvanost, your pics are interesting. I would normally say those spring-dial type thermos are useless but the glass ones you show are exactly what I like to use. Are the 3 HM meters are measuring the same water as the others? That would mean your spring-dial thermo is more accurate than the glass ones. That would be an unusual situation. 

@neo-2fx, nobody will want to hear this but I use whatever crappy heater I have around. I have been through many brands and many individual units and none really stands out as being better. The old Jager heaters were certainly the best - like the Schego or Eheim pumps. Those days are gone and the eheim jagers seem to fail as often as anything else. They do offer top quality glass and a nice heater surface area, so they're still very good in that way. Strangely I still have several working units of the old HGB heaters, cheap in their day and never considered great quality. Perhaps they should start making them again. 

The best thing you can do is have a fish or shrimp room and heat/cool that - you can't realistically cook or chill a tank that way. Second best is to use a quality aftermarket thermostat and just use your aquarium heaters as the heating element - several forum members go that way. 

Edited September 1, 201510 yr by kizshrimp

Thanks for all the replies. Kiz, I'll go have a look today. Salva, I'm guessing those HM TDS pens cost you a fair bit but they seem accurate?

I'd love to have a fish room which the temperature is controlled... If only haha. Where can I get a quality thermostat?

Hi all - similar issue, and I assume I will get similar answers. 

I added a heater to my tank and wanted to keep it at about 22. As advised by my LFS I set it at 24 to then slowly lower it. 

When it was set at 24, the thermostat (which is located on the OTHER side of the tank) was reading 26. I lowered the heater temp by a degree but saw no change. 

After a big rescape yesterday, I put the heater back on at 22, but the tank temp still reads about (again, the thermostat is on the OTHER side of the tank)

ANy thoughts or ideas of what I can do?

Hi all - similar issue, and I assume I will get similar answers. 

I added a heater to my tank and wanted to keep it at about 22. As advised by my LFS I set it at 24 to then slowly lower it. 

When it was set at 24, the thermostat (which is located on the OTHER side of the tank) was reading 26. I lowered the heater temp by a degree but saw no change. 

After a big rescape yesterday, I put the heater back on at 22, but the tank temp still reads about (again, the thermostat is on the OTHER side of the tank)

ANy thoughts or ideas of what I can do?

I think you shluld set up more shrimp tanks.

2 minutes ago, revolutionhope said:

I think you shluld set up more shrimp tanks.

Oh stop it.

But you do raise a solid argument.

Indisputably so

3 hours ago, DemonCat said:

When it was set at 24, the thermostat (which is located on the OTHER side of the tank) was reading 26. I lowered the heater temp by a degree but saw no change. 

Wait ... a heater is not going to cool the tank even if you set it to 22, when the ambient temperature is 26. The tank will be at least the same temperature as the room temps.

What is the weather like in Melbourne?

 

48 minutes ago, jayc said:

Wait ... a heater is not going to cool the tank even if you set it to 22, when the ambient temperature is 26. The tank will be at least the same temperature as the room temps.

What is the weather like in Melbourne?

Yeah I must have underestimated the ambient room temp. Our weather the last week has only been mid-high 20s.

I thought lowering the heater may help as I assumed ambient temp would be high teens but may well be warmer.

Edited February 14, 201610 yr by DemonCat

haha I wish my heaters could cool my tanks too!

Don't forget, pumps from filters will also add a degree or two to the overal temperature.