Your Aquarium Heater Can Be Dangerous: Here’s Why

In Aquarium Heatersby PaulK

Did you know your aquarium heater can electrocute your fish and burn your house down?

You don’t have to search very far to find horror stories about fires with aquarium equipment. These situations occur with surprising frequency. The damages are real and are often catastrophic.

There are in fact things you can do to prevent an aquarium heater failure and prevent loss of fish and damage to your home. The true stories of aquarium heater failures are easy to find. Pictures of these aquarium fires are bound on the internet and these graphic images leave little to the imagination as far as the damage that can be done not only to your hobby but also the risk to your home your family and your pocketbook.

Not all of these aquarium fires and meltdowns are the result of heater malfunctions, however, heaters are the majority contributor to these type of catastrophes. So what are the major contributors to aquarium fires and meltdowns?

Number one is heater malfunction.

Number two is a fish tank pump and motor burn out.

Number three is ballast burns out with fluorescent fixtures.

So why do I feel the need to do an article on heater failures and why do I feel so passionate about it?

I’ve heard and read about many of the painful stories from Aquarists via the internet chat rooms YouTube videos and Facebook. Most recently many of you I’m sure have heard the tragic story of the king of DIY Joey and the loss of his stingrays closer to my own backyard. I have had heater failures myself in the last four years. One of which did result in my losing some prized African cichlids.

One last story.

About two years ago there was a guy on YouTube, let’s call him Bill for a moment, whose dream was to raise tilapia in a 500-gallon tank in his heated garage. I followed this guy’s videos for several months while he set up the tank bought the fish and grew them out only to hear one day that a heater exploded and to view the graphic pictures of 200 dead tilapia at the bottom of his tank. Really sad thing is that a lot of Aquarists like you and I lose their fish and aquariums and have to clean up the damage then swear the hobby off and quit.

Let me share with you what I found to be a common opinion about the failure of aquarium heaters and equipment. Aquarium equipment fails all the time there is no company or product out there that will never fail. Everything is prone to fail eventually. We can do everything we can to prevent it, but at the end of the day, it’s up to you to take the necessary precautions.

You can reduce the risk of a catastrophic heater failure. Let’s first ground ourselves in what is meant by a catastrophic heater failure. Catastrophic heater failure results in loss of fish tank equipment personal property or risk of injury and death to a person.

Let’s imagine for a moment that I am an average Aquarist and I want to buy a heater based on actual input from other hobbyists. As far as which heater is less likely to result in a catastrophic failure in this case I go to Amazon and compare the Cobalt Neo series to the Eheim Jager series of aquarium heaters. we can see that the Eheim has a slightly better rating based on customer reviews and at least on the surface both heater series look pretty darn good.

Next, we dig down a little deeper and we look at the percentage of customer reviews that were bad. Looks like an Eheim is starting to pull ahead in a side by side comparison. Now if we dig deeper yet and actually read the customer reviews there’s an amazing revelation. Nearly all the catastrophic failures were reported by hobbyists for the cobalt neo therm heater.
Eheim 1 star ratings were about difficulties with calibration and temperature control but not catastrophic failures. To summarize my findings based on the detail supplied by Amazon customers we find some amazing and dramatic differences between the two heaters.

Bottom line, the Cobalt heaters are 15 times as likely to experience a catastrophic failure as an Eheim heater.

Here is a short guide to aquarium heaters.

Get a GFCI outlet

Leviton GFNT1-W Self-test SmartlockPro Slim GFCI Non-Tamper-Resistant Receptacle with LED Indicator, 15-Amp, White

GFCI Outlet

GFCI stands for ground-fault circuit interrupter. They are required for building codes where water is near, like a bathroom or kitchen. If your tank is located in a living area, then the outlet is probably not a GFCI outlet. They are safer in that they monitor the amount of current flowing from hot to neutral. If there is a mismatch as small as 4-5 milliamps, it will trip the circuit breaker cutting off the flow of electricity. You can recognize a GFCI by a reset and test button. Also, the left slot is slightly larger than the right slot with a ground hole underneath.

If installing a GFCI outlet is not possible, then consider getting a cover for the outlet to keep out the moisture.

Monitor the water temperature of the tank.

A good investment is a separate digital thermometer, like this cordless jcreate thermometer that sticks to the side of your tank. Worth every penny because you don’t want to rely on the heater-thermometer. Take note of the heater setting vs. the actual temperature of the water. This can tell you if the heater is functioning properly or if it’s over/under heating the tank.

Make sure you have the proper wattage size heater for the tank capacity.
If the heater is too small for the tank, it will run too long and burn out the heater sooner.

When you are going to clean your tank and empty out the water, make sure you unplug the heater 15-20 minutes in advance so the element has time to cool down.

I recommend getting a higher quality heater with a controller that is fully submersible and covered like this Hygger Titanium heater unit that comes with an external controller, and a digital thermometer. It’s also shatterproof. They are a lot more accurate and you don’t have to dip your hand in the fish tank every time you want to adjust the temperature. Some of the cheaper models that have glass cases can be cracked by bigger fish.

Make a drip loop with the cord so water drips off the loop at the bottom into a pie pan or something.

Don’t overload the outlet with multiple plug-in devices. A single outlet can only handle so much wattage. Usually 2400 watts.

If the heater is submersible, then it is OK to have the cord in the water, UNLESS THE CORD IS DAMAGED!

Here are some safety tips to help avoid any danger when using a heater around water. You can reduce the risk of catastrophic heater failure!

A. If the appliance shows any sign of abnormal behavior, immediately unplug from the power source.
B. Carefully examine the appliance after installation. It should not be plugged in if there is water on parts not intended to be wet.
C. Do not operate any appliance if it has a damaged cord or plug, or if it is malfunctioning or if it is dropped or damaged in any manner.
D. To avoid the possibility of the appliance plug or receptacle getting wet, position aquarium stand and tank to one side of a wall-mounted receptacle to prevent water from dripping onto the receptacle or plug. A “drip loop” should be arranged by the user for each cord connecting an aquarium appliance to a receptacle. The ”drip loop” is that part of the cord below the level of the receptacle or the connector if an extension cord is used, to prevent water travel along the cord and coming in contact with the receptacle. If the plug or the receptacle does get wet, DON’T unplug the cord. Disconnect the fuse to the circuit breaker that supplies power to the appliance. Then unplug and examine for the presence of water in the receptacle.
E. Close supervision is necessary when any appliance is used by or near children.
F. To avoid injury, do not contact moving parts or hot parts such as heaters, reflectors, lamp bulbs, and etc.
G. Always unplug an appliance from the outlet when not in use, before putting on or taking off parts, and before cleaning. Never yank the cord to pull the plug from the outlet. Grasp the plug and pull to disconnect
H. Do not use an appliance for other than intended use. The use of attachments not recommended or sold by the appliance manufacturer may cause an unsafe condition.
I. Do not install or store the appliance where it will be exposed to the weather or to temperatures below freezing.
J. Make sure an appliance mounted on a tank is securely installed before operating it.
K. Read and observe all the important notices on the appliance.
L. This Appliance has a polarized plug (one blade is wider than the other). As a safety feature, this plug will fit in a polarized outlet only one way. If the plug does not fit fully in the outlet, reverse the plug. If it still does not fit, contact a qualified electrician. Never use with an extension cord unless plug can be fully inserted. Do not attempt to defeat this safety feature. M. If an extension cord is necessary, a cord with a proper rating should be used. A cord rated for fewer amperes or watts than the appliance rating may overheat. Care should be taken to arrange the cord so that it will not be tripped over or pulled.

You can never be too safe when it comes to electricity and water, so take the proper precautions or you may be sorry!

So what are the key takeaways?

The first takeaway is for mission-critical aquarium components like heaters. Buyer beware. They can do a lot of damage if you pick the wrong brand.
The second key takeaway is that information is readily available to help you determine heater failure rates.
Lastly, heater brand selection can have a major impact on reducing your risk of a catastrophic heater failure. A few key questions I’d like to leave you with: Is your heater brand model reliable? Is it safe? and ask yourself the question: should it be replaced?

Recommended equipment for your aquarium


The thermostat inside is like a little switch. It can stick on or it can stick off depending on the type and/or time of year, depending on your climate. Either one could be potentially catastrophic.

If it sticks on at any time of year that’s not good because if it’s a good size heater for what you have for your tank, you’re going to cook your fish. If it sticks off and you live in a cooler climate and it’s wintertime, the water could get cold enough to a point where they could pass away.

Why does this happen?

I think it’s just simply in the design. I’m no engineer. I’ve never taken one apart to figure out what’s good or what’s not. A seal goes bad and water touches the heating element and the electronics and that could either short-circuit and electrocute things or it could flush that water back out to the system nuking the tank.

There was a particular brand of heater for a while, Marineland stealth, a black plastic heater not to be confused with the new ones that make plastic heaters. Marineland is the first that ever did the whole plastic encased heater which seemed like a good idea. Unbreakable and less expensive than the titanium versions. The problem was that they literally exploded like a grenade and released a ton of toxins into the tank. I’ve even heard of some stories and saw pictures where they actually exploded and took out the sump at the same time. It was a horrible, horrible mess so if you have one of those get rid of it.

So how do we kind of plan ahead for these failures? How can we prevent having to deal with this issue? Well picking a good heater helps. It doesn’t have to be the most expensive kind. I’ve had very very good luck with the Hygger Titanium. I’ve used those for a lot of builds over the years. I like the fact that it has an external temperature controller so you don’t have to dip your hand in the tank every time. They’re just a reliable heater and they’re shatterproof. They go for years and years and the percentage of those that I’ve had to go bad on me over the years is a fraction of any of the other brands.

Beyond that, they make things such as heater controllers and I’m not talking about the big expensive ones. They have controllers that’s all they do is just control your heater. That would be a great way to buy a little bit of insurance. They can’t be affected by water getting in for one. If the switch sticks on in the heater it can’t cook your tank because the heater controller controls when it goes on and off. You typically set the temperatures too high and then the controller dials in when to shut it on and off based on the preset temp. They have a separate probe that you can place elsewhere in the system so instead of relying on the thermostat that’s inside the heater localized in that little area you can put it elsewhere and get a more true reading for what the tank’s temperatures really is. So those two things, a good quality heater for one and then a heater controller. The grand total between the good heater and a heater controller you’re probably going to be up around 100 bucks if not more. It just seems like a small price to pay to have one less thing potential to go wrong.

When it comes to fishkeeping, what is your single biggest challenge or frustration? Leave a comment below.

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