The Puffer Forum

Ok guys, sorry you don’t see me much but its been awhile I know….

Ill explain in as fast a way as possible…. I purchased some new heaters, vistherm ones. I set the temp to 77 on both my 30 gallon and my 60 gallon. The heaters internal temp monitors seem to be reading colder than my traditional mercury suction cup heaters do? After adjusting the heaters to try to prevent the water from getting to hot….. In fact the 60 gallon visitherm is set at 74 and the mercury thermometer was reading at almost 80! My 30 gallon one is a little better with the mercury reading at 77 and the heater set at 74?

Its almost like the visitherm heaters are not calibrated or something? I am afraid because I do not know which reading to trust? And if the visitherm heaters are already not acting right is there a danger of a malfunction and a cook off? I live at a high elevation… a little above a mile over sea level. Does elevation effect heaters?

I bought these damn things from petmountain and do not want to have to go thru the trouble of return shipping and all that? Will they eventually calibrate properly or could my mercury traditional thermometers be wrong? They are old, do those need to be replaced? Thanks in advance guys!

define999 wrote:In fact the 60 gallon visitherm is set at 74 and the mercury thermometer was reading at almost 80!

If you want the tank temp at 78, then set the Visitherm at 72...And so on.




Most heaters are off by at least several degrees. It is best to set the heater by adjusting it up or down till the mercury thermometer is where you want it. My old Visatherm is off by like 8 degrees. My old Italian Stealth Pros are with a degree or two. Others are of by more.
I have a Eheim Jager heater that can be calibrated...But it is not calibrated because I just go by the actual tank temp.

It used to be heaters didn't have numbers on them. I think it is just a marketing thing because one manufacturer did it so the others had to follow suit.

Ignore the numbers on the heater. Slowly make adjustments on the heater up or down until the mercury thermometer is where you want it.

my visi-therm heater temp readings is not even working. i only use it to premix salt water and its still working well. i always base the temp off the traditional thermometers.

Maybe it's your thermometer?

Thanks for the responses guys! So far the temo has held, even though it doesnt match the fron temp reading.... fingers crossed....

Do those old school style mercury thermo's go bad Pufferpunk? I thought maybe I could go buy another 2 and put them in the tank and if they read the same as the older ones I have then they cannot be bad right?

Expecting "true calibration" from common single-tube tank heaters is wishful thinking. Among other things, few tanks are totally uniform in current or temperatures. In a new set-up or with a replacement heater, I use several electronic thermometers to get and check the temperature and its uniformity. I have not used any mercury (or alcohol) thermometers in tanks in years. They are not safe,

define999 wrote:Thanks for the responses guys! So far the temo has held, even though it doesnt match the fron temp reading.... fingers crossed....

Do those old school style mercury thermo's go bad Pufferpunk? I thought maybe I could go buy another 2 and put them in the tank and if they read the same as the older ones I have then they cannot be bad right?

You can generally repair them by heating vertically in a pan of water - obviously you prop it up so you don't burn your hands at the same time!

Alcohol can degrade/dissipate over time but the downside to mercury ones is that they are toxic. Both are perfectly safe if you don't break them!

I use the alcohol ones now because I don't want to spend ludicrous amounts on electronic ones, I did have some cheapo electronic ones at one point but the readings that I got from them were all over the place and so went to the same place as my chocloate fireguard.

I use the stick-ons.

Iliveinazoo wrote:

define999 wrote:Thanks for the responses guys! So far the temo has held, even though it doesnt match the fron temp reading.... fingers crossed....

Do those old school style mercury thermo's go bad Pufferpunk? I thought maybe I could go buy another 2 and put them in the tank and if they read the same as the older ones I have then they cannot be bad right?

You can generally repair them by heating vertically in a pan of water - obviously you prop it up so you don't burn your hands at the same time!

Alcohol can degrade/dissipate over time but the downside to mercury ones is that they are toxic. Both are perfectly safe if you don't break them!

I use the alcohol ones now because I don't want to spend ludicrous amounts on electronic ones, I did have some cheapo electronic ones at one point but the readings that I got from them were all over the place and so went to the same place as my chocloate fireguard.

even with highly controlled heating/cooling you can still get a break in the Hg/alcohol stream leading to inaccurate readings.

Back in the dark ages, I used Hg/alcohol thermometers in-tank 24/7. They were the only available option, there were no other options on the market.

Now I do not have and will never again have any Hg/alcohol thermometer indwelling in any of my tanks. That is ancient history and is not worth the risk. For me, a broken mercury thermometer require discarding most of the set-up to avoid risk to myself and/or the fish. NIMFT, not ever again.