# Hydor ETH-300 Overheated and killed my fish



## tropicalfish (Mar 29, 2007)

Hello everyone! Haven't been here in a while.

Anyway, I checked on my tank today and found a TON of dead fish everywhere, in plants, on intake strainers, on the surface, etc. And the tank was hot.

I looked at my thermometer and it was nearly 100°F. 
Since the dead fish were white and their eyes were pretty much gone, I could have only assumed that it happened like yesterday or something, when I didn't get to check on the tank.
Anyway, the heater was warm and the red LED was off. I'm not sure if the heater is still functioning (if the element burned out or if the temperature sensor died), but I'd rather not risk using it again.

Anyone else with a similar experience? Does Hydor have a warranty? And if so, how long?

Thanks.


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## xmas_one (Feb 5, 2010)

Wow, what size tank did you have it in? I always try to run the smallest heater possible just in case.


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## CL (Mar 13, 2008)

Send Hydor an email


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## cheaman (Jan 22, 2009)

I'm running an inline hydor 300 on my 125 and haven't had any issues (so far). How old was the heater?


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## comatoast (Mar 11, 2009)

Yikes! My ETH seems so reliable and consistent- this is scary...


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## TLE041 (Jan 16, 2010)

That's scary. I have a 200W one on my 4 gallon nano. I only have it plugged in the winter when it's needed.


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## deeda (Jun 28, 2005)

Very sorry for your fish loss. I too am curious what size tank this was on, how long you have had the heater for and whether or not the heater was mounted vertically.

BTW, the Hydor warranty is 24 months from purchase date and for defects in material or manufacturing defects only.


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## lauraleellbp (Feb 3, 2008)

So sorry about all your losses! 

IME it's really easy to bump the dial on the thermostat and move it by accident, so I'd check that setting too.

IME Hydor ETHs as a whole are pretty reliable. Equipment malfunctions are always possible with anything though.


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## xmas_one (Feb 5, 2010)

TLE041 said:


> That's scary. I have a 200W one on my 4 gallon nano. I only have it plugged in the winter when it's needed.



That's crazy, why such a big heater on such a small tank?

I'd have a 25/50 watt heater on that thing, max.


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## captain_bu (Oct 20, 2007)

lauraleellbp said:


> IME it's really easy to bump the dial on the thermostat and move it by accident, so I'd check that setting too.


x2...

Check the temperature setting. This is the most common reason for problems with the Hydor's. Lots of folks put a piece of tape over the thermostat control once it is set so the dial can't turn if it is accidentally bumped. 

As deeda points out the Hydor's also need to be mounted vertically though I believe that is to prevent any air getting trapped and causing the heating element to overheat and burn out. Doubt that would cause overheating of the tank itself just failure of the heater.


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## EdwardN (Nov 7, 2008)

When one uses a heater in May, what one uses in Winter?


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## lauraleellbp (Feb 3, 2008)

EdwardN said:


> When one uses a heater in May, what one uses in Winter?


A stove?

It was snowing last week in Denver though...


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## tropicalfish (Mar 29, 2007)

It was on a 75 gallon.


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## tropicalfish (Mar 29, 2007)

So apparently the heating element isn't dead. The temperature sensor seems to work also...Not sure if I would trust the heater again, though.


EDIT: Oh, and about the adjustment knob--that's been taped down for a long while.


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## Oreo (May 6, 2008)

The hydor ETH series (and probably all aquarium heaters) use a mechanical relay to switch the heating element on & off. Mechanical / magnetic relays can and do fail. Knowing that, it's not something I worry about with my ETH but if I had a lot of expensive fish I'd definitely look into a secondary back-up temp controller just for insurance.


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## fox (May 16, 2006)

Sorry about your losses.

It musta went higher than 100°f then if the unit was off when you noted the temp. I have two eth300's onna 210 but have them set a few degrees apart so only one is really ever working. The only time I ever see them both on is after WC's or very cold NE weather.

Always wondered how high the temp would go if one failed :eek5:


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## tropicalfish (Mar 29, 2007)

It turns out the temperature sensor still works, but the mechanical relay somehow stuck, even though I see no way it would have turned on. I probably would just start leaving the heater switched off entirely during the summer.

That means, if I plug it in and turn the knob, the red LED would turn on when appropriate. However, there is no "click" sound and if I plug one end and fill the unit with water, set the temperature to the lowest, and plug it in, it will still heat the water.


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## cott (May 26, 2007)

Oreo said:


> The hydor ETH series (and probably all aquarium heaters) use a mechanical relay to switch the heating element on & off. Mechanical / magnetic relays can and do fail. Knowing that, it's not something I worry about with my ETH but if I had a lot of expensive fish I'd definitely look into a secondary back-up temp controller just for insurance.


Heaters too small with too little wattage only burn up. You need enough watts to actually warm the water. A small heater will only turn off and never shut back down because it will not reach the desired temp.


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## tropicalfish (Mar 29, 2007)

Thank you Hydor for replacing my heater.


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## bluecheese (May 22, 2009)

Man, that sucks. I small suggestion though. Get a digital thermometer that beeps when the temperature fluctuates too rapidly. It may not save your fish if the heater goes haywire when you're not home, but it may let you catch the malfunction in time.


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## wendyjo (Feb 20, 2009)

TLE041 said:


> That's scary. I have a 200W one on my 4 gallon nano. I only have it plugged in the winter when it's needed.


Holy cow 200 watts on 4 gallons?


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## Guest (Oct 8, 2013)

*My Hydor ETH 300W malfunctioned today*

The thermostat went bad today and the water temperature kept rising. One Cory died , but the Discus were fine. The water temperature had reached 92.4 F. I was lucky that my wife noticed the flashing temperature range on the Hagen G3 filter and unplugged the heater. Now I am looking for a more reliable inline water heater. Sure not buying this product any more.


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## jimmyjam (Dec 25, 2008)

i just had the exact same problem on my 49 gallon with the 200 watt. Im furious and can not fix the problem


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## PlantedRich (Jul 21, 2010)

This is not unusual but more what I expect. I no longer run any tank with fish that I consider "valuable" without a temperature controller as a fail-safe. ALL mechanical /electrical items fail at some point. 
For those who run without, consider you've been warned?


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## devilduck (May 9, 2012)

Wow sorry for your losses. Somewhat comforting to know that Hydor replaced your heater. 

The I have the 200w and fried some sensitive fish because I accidentally bumped the temperature dial during a filter cleaning. Otherwise it's been running great. Now I want to go buy a temperature controller just in case.


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## giorgiot (May 24, 2015)

*very sad*

Hallo Guys,
I found this thread looking for "hydor failure".
I've had a eth200 fault this night that killed my water turtle 10 years old.

I'm very sad for my turtle.

hydor, such a [censored][censored][censored][censored]


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