10 Gallon Tank Safe temp change? heater and temp questions

  • #1
Okay I have a 50w eheim Jager Heater (brand new) and after calibration I let it run for a week... trying to get 75 deg F but it drops down to 74.7 then jumps up to 76.2 once per hour... that's 24 times it changes per day like that... Is this normal heater operation to move a 1.5 deg during heating? Keep in mind my fish tank is in a 72 deg room with LED lights. Nothing that will heat up it. Also I have the heater Horizontal with the filter above it. Should I freak out and buy the best fish tank heater known out there? If so what's the best. I can have a glass one, my fish lay near my heater they don't ram it or anything weird.

ALSO ive tried 4 digital thermometers and all of them vary in there own calibration give or take 1-4 deg F Each are diff brands.
Same happened with glass ones... All are from China and one from Taiwan. I had them side by side and even dropped them into the cold air and they still were off from each other after an hour... But they all agreed the tank temp was changing fast and a lot...

Sorry for the lot of questions.
Thanks ~Ben
  • #2
Hi, welcome to Fishlore

What is the ambient room temperature? It could be causing the temp to fall quicker than normal.
Where is the thermometer placed? The temp change will be more evident the closer the thermometer is to the heater

To be honest, I've never looked at the temperature swings between heating cycles, but it sounds a bit odd. A 50W heater in a 10G tank is probably a little over-kill (5W per gallon), and may be causing rapid heating.

It is also possible that the heater is faulty - I'm hearing more and more reports about the (poor) quality of Jager heaters recently. Eheim changed things up to meet pricing pressures in the market, and are now suffering in the quality stakes
  • #3
Eheim probably *is* the best aquarium heater out there. I have two and I absolutely love them.

So, first question, how big is your tank? Temperature swings are much wider in a small tank as opposed to a larger one.

Secondly, 1.5 degrees is really not that big of a difference in temp. Water temperatures vary probably much more than that throughout the course of a day in your fish's native habitat.

I have small tanks personally, my largest being a 20 gallon that's not even full. I would guess that my tanks vary up to 2 degrees in temp per day and my fish have never had any health issues because of it. Some of the fish I keep are very sensitive as well, so that's some food for thought.

Edit: Most of the reports I hear about the Jager heaters being faulty seem to be due to people not being able calibrate them properly. Just more food for thought
  • #4
Sounds like the thermostat is operating normally. Apparently dropping about one degree Celsius before turning on and heating it up a degree before shutting off.

At one time I kept a log of aquarium temps with a very precise thermometer and my Jager heaters behaved like that and almost all of the other ones dropped much further before coming back on. There were a couple that varied by five degrees Fahrenheit and I decided to retire them to my emergency supply box.

This is why you don't want to have a heater that is too high of wattage for your tank, because it heats the water back up too fast and stresses the fish. A weaker heater changes the temperature much more gradually. Of course, too weak of a heater does it too slowly or doesn't get up to the proper temperature at all.
  • Thread Starter
  • #5
So the temp change is okay just not that fast of rate per hour. What should I have? 25w? Or is this not enough to really worry about
  • #6
It's fine. Mine do the same thing and my fish are all fine with it.
  • #7
I think 50w is right for a 10g, that's what I have in mine and I wouldn't worry about that temperature change either, it's not too big.
  • Thread Starter
  • #8
That's what I hoped youd all say. Now if it changed over 5 f then id have a problem. Most my fish are diehards (45°f to 82°f) besides my clown pleco. But I haven't seen her since I bought her so who knows. Anyway ill find a nice calibrated thermometer soon when I can. Also my whole tank is within .1°f there are no hot spots. Water is flowing alot. All my fish are river fish

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