# Hydor Theo heater?



## finnfinnfriend (Feb 3, 2012)

It seems like a number of people have poorly calibrated Hydor Theo heaters...myself included. Does anyone out there have an accurate one? One that stay at least 2 degrees of where you set it? I would really like to know that the majority of these heaters work well, because I really like how small they are and that they are fully submersible. I would like to trust that if I bought a new one it would be better than my current one.


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## lilnaugrim (Mar 27, 2013)

It's not about the calibration. Often with heater's regardless of size, they like to overcompensate so when you set it at 76, perhaps it reads on your thermometer at 80. That is completely normal and has nothing to do with the calibration of the heater, much of it has to do with how hot or cold it is outside the tank as well and what size/how many watt's of heat you have. Typically I find that if I have a 25 Watt heater which is usually rated under 10 gallons but have it in a 15 or 20, it will have a more accurate "reading" but if you put it in the suggested 3-10 gallon space, it will read higher than what you actually set it at. It's all part of just being a heater and it's not just the Hydor's that do this, all adjustable heaters do depending on the circumstance of course.

So this is why having a thermometer is extremely important, that and to know if your heater is just doing crazy things. Heater's generally don't heat more than 3-4 degree's higher or lower than you set it so if it's going up like 10 degree's or more, it's most likely malfunctioning. Same with if it's dropping and going higher again constantly. Your heater is working when it keeps it at around one temperature so set for 78 but heats at 80 and then flucts between 78-82, that's normal.


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## finnfinnfriend (Feb 3, 2012)

My room is really hot though and it's still over. And it's a 25w in a 5.5 gallon.


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## Quinn (Apr 4, 2010)

My 25w Hydor has kept my 6.5 gallon long tank where I set it, provided the room itself isn't very hot, in which case obviously it will raise the temp. I keep my heater set right around 80, and my tank was pretty consistently at temp.


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## finnfinnfriend (Feb 3, 2012)

Quinn said:


> My 25w Hydor has kept my 6.5 gallon long tank where I set it, provided the room itself isn't very hot, in which case obviously it will raise the temp. I keep my heater set right around 80, and my tank was pretty consistently at temp.


Good to know. Thanks


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## lilnaugrim (Mar 27, 2013)

Yeah, that's another thing. If the outside temp is hotter, it might overcompensate since it doesn't know that and the water is generally cooler than the air anyway. And then if the room is colder, it tends to stay around where you set it


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## finnfinnfriend (Feb 3, 2012)

For me, it doesn't matter whether it's cold or hot or whatever....idk its weird...


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## OrangeAugust (Jul 23, 2012)

I have a 200 Watt in my 55 gallon (the size that's recommended) and I have to set it at 74 in order for the water temp to be lower than 82. I have 2 others and they're also pretty much the same- they run warmer than what they're set for.


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## finnfinnfriend (Feb 3, 2012)

I honestly think I will just go wih Eheim Jager heaters from now on...


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## lilnaugrim (Mar 27, 2013)

Yeah but it's happened with pretty much every adjustable heater I've owned, it's not just the Hydor's.


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## Briz (Mar 22, 2013)

I've used 3 of the Hydor Theo heaters and they kept the water temperature in the range they were set. I'm sure some can be hit or miss.


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## finnfinnfriend (Feb 3, 2012)

I'm sure they are hit or miss, but after reading online reviews for both, the Eheim seems to be much more reliable and accurate. There is also a calibration knob on the Eheim so you can manually calibrate it if it is a little off out-of-the-box.


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## hopeful fish (May 29, 2013)

I have 2 heaters. If I set one at 75, the temp is at 79. With my other one, if I set it at 76, the temp is at 79. As long as you pay attention the first few days, the hydor will hold it steady once you set the temp.


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## finnfinnfriend (Feb 3, 2012)

So you guys think the Hydor is as good as the Eheim?


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## Briz (Mar 22, 2013)

No, Eheim should be better quality. But Eheim heaters are not small like Hydor Theo. Hydors are best suited for nano tanks or bowls where a regular sized heater would be too long or take up too much space.


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## finnfinnfriend (Feb 3, 2012)

An Ehiem would fit in my 2.5 gallon....Probably not in a 1 gallon bowl though.


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## lilnaugrim (Mar 27, 2013)

I'm also looking at price tags lol I'm a college kid addicted to Betta's sooooo....yeah Hydor's for me ^_^ It does come down to personal preference though when you can afford any which heater's or just really want one over the other. They both do the same thing and both require a thermometer with way so for me, it's just a personal choice. I like Hydor's mostly because of the size and the price tag is all.


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## finnfinnfriend (Feb 3, 2012)

lilnaugrim said:


> I'm also looking at price tags lol I'm a college kid addicted to Betta's sooooo....yeah Hydor's for me ^_^ It does come down to personal preference though when you can afford any which heater's or just really want one over the other. They both do the same thing and both require a thermometer with way so for me, it's just a personal choice. I like Hydor's mostly because of the size and the price tag is all.


Yeah I really wish that the 25w Eheims were the same size as the Hydors of the same wattage....But the Eheims are only $5 more lol....And I am so poor I am a starving COMMUNITY college student and I don't care lol


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## lilnaugrim (Mar 27, 2013)

5 dollars goes for my gas for my truck though haha. But yeah, I understand, I go to a university but it's in state and only 20 minutes from my house so it was the cheapest option.


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## finnfinnfriend (Feb 3, 2012)

lilnaugrim said:


> 5 dollars goes for my gas for my truck though haha. But yeah, I understand, I go to a university but it's in state and only 20 minutes from my house so it was the cheapest option.


I am really stupid with money too so....yeah....lol XP


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## lilnaugrim (Mar 27, 2013)

finnfinnfriend said:


> I am really stupid with money too so....yeah....lol XP


Yeah....me too >.< oh well, we only live once right? lol ;-)


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## finnfinnfriend (Feb 3, 2012)

lilnaugrim said:


> Yeah....me too >.< oh well, we only live once right? lol ;-)


YOLO! lol jk.....But it's true! Do you know how many times I said "you only turn 21 once" on my 21st birthday? Me neither....lol


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## lilnaugrim (Mar 27, 2013)

finnfinnfriend said:


> YOLO! lol jk.....But it's true! Do you know how many times I said "you only turn 21 once" on my 21st birthday? Me neither....lol


LMAO! Yeah, I'm sure I'll be saying that soon! My birthday is coming up quickly and on a Wednesday night of course! Thursday is going to be...fun and then we do it all over again, same with Friday and then Saturday is party all night day since I'm two day's older than my cousin so we'll both be celebrating hard that Saturday night! Uggg I'm going to die >.< But hey, free alcohol! lol


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## finnfinnfriend (Feb 3, 2012)

lilnaugrim said:


> LMAO! Yeah, I'm sure I'll be saying that soon! My birthday is coming up quickly and on a Wednesday night of course! Thursday is going to be...fun and then we do it all over again, same with Friday and then Saturday is party all night day since I'm two day's older than my cousin so we'll both be celebrating hard that Saturday night! Uggg I'm going to die >.< But hey, free alcohol! lol


Lol have fun!


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## lilnaugrim (Mar 27, 2013)

hehe thanks ^_^ it should be interesting regardless!


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## jadaBlu (Feb 14, 2013)

I was able to use a small hydror yesterday to heat a one gallon to a consistent temp for a sick fish in a critter carrier. Many heaters are not good for one gallons and this heater is rated to heat a bigger tank but it's staying consistent.


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## FirstBetta (Jun 14, 2013)

If you read the Specs for any heater even the most expensive you will see something in the order of "will maintain temperature +/- 2 to 3deg F or C". That means that the temp can fluctuate 4 deg over all or 2 deg + or -.

I'm not sure but I would guess that any heater that would be more accurate would be out of the budget of most hobbiests, my self included.

I have a Fluval E model which displays the set point and which is at the top of my budget and it reads about 2 degrees cooler that the thermometer reading.

Then there is the tolerance of the thermometer reading. I have three digital thermometers, one for each tank, and they all read difference when in the same tank. The reason I got the digital ones is I couldn't even read the glass ones due to my eyesight.

From my research it seems that the important info is how constant the temp stays. I live in the high desert of SoCal. I have Air conditioning, I wouldn't survive without it since the temp outside is at the 90's with frequent jumps to 100+. I set the house thermostat at 78 and my tanks heaters hardly come on except in the early morning when the outside temp drops in to the 70's. And then infrequently. I found a thermometer at Dr. F&S that is a laboratory standard type it reads about 2 deg
cooler than the digital thermometer in each tank. It is supplied with a calibration chart with certified readings at freezing and boiling which is how most thermometers are calibrated.


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## finnfinnfriend (Feb 3, 2012)

FirstBetta said:


> If you read the Specs for any heater even the most expensive you will see something in the order of "will maintain temperature +/- 2 to 3deg F or C". That means that the temp can fluctuate 4 deg over all or 2 deg + or -.
> 
> I'm not sure but I would guess that any heater that would be more accurate would be out of the budget of most hobbiests, my self included.
> 
> ...


So you are saying that if I like the size of the Hydor, I should just stick with that rather than switching to a Jager?


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## FirstBetta (Jun 14, 2013)

*Hydor heaters*



jadaBlu said:


> I was able to use a small hydror yesterday to heat a one gallon to a consistent temp for a sick fish in a critter carrier. Many heaters are not good for one gallons and this heater is rated to heat a bigger tank but it's staying consistent.


The heater MFR'S are doing us a disservice by saying the heaters are for a max size tank. All the heater does is heat up the water to the point where the bimetallic switch will open and shut the heater off. If there is physical room in the tank you could put a 300W heater in a one gallon tank and it would operate to the set point and shut off and then come on again when the temp drops below the set point band. And the tank inhabitants would not know that there is a 300W heater in the tank because it would be in the temp range for them.


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## finnfinnfriend (Feb 3, 2012)

FirstBetta said:


> The heater MFR'S are doing us a disservice by saying the heaters are for a max size tank. All the heater does is heat up the water to the point where the bimetallic switch will open and shut the heater off. If there is physical room in the tank you could put a 300W heater in a one gallon tank and it would operate to the set point and shut off and then come on again when the temp drops below the set point band. And the tank inhabitants would not know that there is a 300W heater in the tank because it would be in the temp range for them.


Oh I didn't mean size as in wattage, I meant the physical length. The Hydor is two inches shorter than the Jager.


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## finnfinnfriend (Feb 3, 2012)

I guess the Hydor Theo isn't a bad heater and I like how nicely it fits in my 2.5g


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## FirstBetta (Jun 14, 2013)

finnfinnfriend said:


> So you are saying that if I like the size of the Hydor, I should just stick with that rather than switching to a Jager?


NO! I'm just laying out the reality of the aquarium heater world. The choice of heater is often a very personal decision and I have no right to tell you what to do.


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## finnfinnfriend (Feb 3, 2012)

FirstBetta said:


> NO! I'm just laying out the reality of the aquarium heater world. The choice of heater is often a very personal decision and I have no right to tell you what to do.


Oh okay.


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## NorthernLights (Mar 2, 2012)

I've had three Hydor Theo heaters. My original trusty 25 watt gave out last week (actually, it started heating out of control, fortunately I noticed when the water was at 90 degrees and the thing was still heating, and Galahad was still alive. I tried fiddling with it, but it seems to have become stuck in the heating mode on any temp. Before that, I had needed to turn it way down for about a week to keep the temp down at 80ish...now I know why. Prior to that, it had been very trusty. My 50 watt (which is in a 3 gallon) works great, I keep it turned just a touch down (it's on ~78, keeps the tank right at 80). The new 25 watt I got for Galahad's 1.75 gallon, which just got upgraded to a 3 gallon, is on about 79 degrees and keeps it right at 81. 

They are not perfect, but they are great little heaters. Nice and small, fitting in even tiny aquariums. I find I do need to re-calibrate them depending on the season (so in winter, when my apartment is always quite cool, maybe 60-65 degrees, I turn the heater up to 84 or so to keep things on 80, and when it got hot, I turned them down to the upper 70's to keep things on 80ish. I will agree they like to heat to 82 unless you are really watchful about calibrating juuuuuuust right.


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