25 Watt Heater Managing To Overheat

PascalKrypt

So I bought this heater, a fluval preset (to 78, I was told when buying), second-hand (guess I know now why it was being sold, whoops) but it has been doing something puzzling. Even though it only has 25 watts of powerhouse, it overheats even my 10 gallon to a whopping 86F.

Weirdly, it seems that it is actually the thermostat that is broken, not the heater itself. Because it heats anything to exactly 86F, I tested this in a 2.5, 5.5 and a 10 gallon. I don't have an empty 10+ without plants that would prefer not to be fried so I can't try any larger.

Should this be possible at all? I thought the limit of a 25 watt was pretty much 10 degrees in a 5 gallon or 5 degrees in a 10 gallon. My room temp is at 68-69, so it is heating a 10 gallon close to 20 degrees.

I've had it on for a while so it isn't like it is burning out either, and it does actually stop heating when the temperature reaches 86. Back in the summer when the room temperature exceeded 86 it stopped heating for several days until temps dropped again, so I didn't actually notice for a while how wonky it was. Now that autumn has come again I'm baffled it is managing to maintain that temperature.
(When I noticed what was going on with it I put it in an empty tank, so nothing is getting fried in there. I could toss it but it does function consistently so is there any fish that wouldn't mind that temp or should I just put it in a well-circulating 30 gallon and save on buying a more powerful heater?)
 

Heron

I have never had a heater which actually stopped working, just the thermostats become less stable ( the gap between the on and off temperatures gets bigger so the temperature fluctuates more ) or the adjustment knobs stop doing anything, which sounds like the one you've got.
Although heater manufactrers say 1 watt per liter I have found that this is far more than necessary even in my room which is quite cold.
I have a 120 G tank with 2 150W heaters set 1 degree apart. My room temp is 12 degrees below the tank temp and the second heater never comes on. I just have it in case the main heater dies.
 

pagoda

I strongly suggest replacing it asap with a brand new (and guaranteed) heater cos the last thing your fish...or you...need is to be dealing with an exploding heater as was the case with someone else on the site a couple days ago.
 

Heron

I agree with pagoda, a new heater is not expensive and it's not worth risking you fish to save a few quid. It's best to check your temperature at least every morning and evening and if there is a problem you can catch it quickly. I would always recommend to have a spare heater in case one fails on a day you can't easily get another. As your heater kind of works why not make it your emergency spare.
 

nikm128

Aqueon has a lifetime warranty, essentially no questions asked other than what the issue is. They could be more accurate but they're not bad heaters at all.
 

Heron

I find most heaters die after a year or two regardless of brand or price so if you can get one with a lifetime warranty I would go for it.
 

PascalKrypt

I strongly suggest replacing it asap with a brand new (and guaranteed) heater cos the last thing your fish...or you...need is to be dealing with an exploding heater as was the case with someone else on the site a couple days ago.
o.o wut? That happened to someone, just spontaneously? I thought that only happened when people forgot to unplug during a water change...
I agree with pagoda, a new heater is not expensive and it's not worth risking you fish to save a few quid. It's best to check your temperature at least every morning and evening and if there is a problem you can catch it quickly. I would always recommend to have a spare heater in case one fails on a day you can't easily get another. As your heater kind of works why not make it your emergency spare.
I think I'll do that.
Aqueon has a lifetime warranty, essentially no questions asked other than what the issue is. They could be more accurate but they're not bad heaters at all.
I haven't had a heater failure yet (don't think this one counts as it did not work properly from the day I got it), but I'll keep that in mind if it does happen to me.
 

PascalKrypt

Take a look at this thread, about halfway through his heater went bang inside the aquarium

Heater Cracked Help | Heaters 423418
Hmm, the video linked mentions this won't happen to ceramic heaters and the fluval heater in question is a ceramic one (it looks like a solid black block, I actually bought it because I thought it looked neat).
Scary stuff though. I think I have one of those heaters of that brand... I'll have to check my tanks to see where it is owo
 

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