Heaters – The Ticking Timebomb in Every Tank

Heaters are one of the most overlooked pieces of equipment in this hobby. They are the number one cause of tanks crashing. This is very unfortunate because they are actually one of the most affordable pieces of equipment and something we have the most control over.

The problems with aquarium heaters are:

  • They are VERY oversized for the tanks they are recommended for
  • They fail
  • They usually fail on
  • They have no built-in redundancy
  • Glass ones leak or even crack
  • Glass ones look bad

Solutions in order of importance

  • Never run a “properly-sized” heater. Always run them weaker. Most heaters are rated for somewhere around 5 watts per gallon. Most tanks only need about 2 watts per gallon unless your home is unusually cool. This extra strength means that if/when the heater fails on, it is more than powerful enough to overheat the tank to lethal levels.
  • Split those 2 watts per gallon into two separate heaters so that if one fails on, the other can just stay off and neither can overheat the tank on its own. Also, if one fails off, the other can stay on and minimize the temperature drop.
  • Replace heaters regularly. No matter which heater you choose, it cannot be trusted 100%. Sooner or later it can fail and it makes no sense to risk hundreds or even thousands of dollars in livestock to $100 worth of heaters. Whether you choose to replace them every year, or if you have multiple heaters run on a controller which provides more redundancy and are okay letting them go to every two to three years, don’t just sit back and wait for them to become a problem before you replace them. You don’t wait for your engine to blow up before you change the oil in your car, don’t wait for heaters to be a problem. An ounce of prevention is worth a ton of cure.
  • Have a separate thermometer that’s easy to read. Ideally, it is digital and even illuminated so that you can check it at a glance while walking by the tank and not even have to think about it.
  • Use a controller. Set the heaters to two degrees above where you actually want the temperature so they always come on when the controller turns on, then set the controller to the actual temperature you want. This means the heaters will turn off if the controller ever fails and tries to run them more than it should (such as if the probe comes out of the water). You have all the redundancy of multiple undersized heaters plus the added redundancy of a controller that can cut them all off if it gets too warm.

What is the Best Aquarium Heater?

This is a tough question because when you ask something like this, you don’t get a real answer, you just get a survey of what people are using that hasn’t been a problem for them yet. No one actually tests ten different heaters and determines which one is best. And how do you define best? Strongest? Least temperature variation? Lowest cost while still being “reliable”? Most expensive? Most bells and whistles? Glass? Titanium? External controller? Separate probe? Does any of this even make a difference?

The reality is that all heaters will do their job well, until they don’t. So how do you decide? Here is what I like and why:

No Glass

Glass is just too fragile and looks ugly. I paint the backs of my tanks black and the last thing I want is some ugly glass heater distracting from enjoying the fish and aquascaping. They are also fragile and more prone to leaking. The last thing I want is to have to replace a heater because I bumped it the wrong way, a piece of décor fell on it, or some big fish enjoys banging it against the wall. None of these are benefits to me, so I have no desire to ever use any type of glass heater, not even the almighty Eheim.

No Titanium

Again, I paint the backs of my tanks black and I don’t want a metal rod distracting from the aesthetics of the tank. There is nothing wrong with titanium on its own, it just looks bad (although I’ll take it over glass any day). So if I was buying heaters for a sump, I wouldn’t care whether it was titanium or not, only if it will be in the display. Be aware that because titanium is a hot trend in heaters, there are lots of cheap titanium heaters just trying to ride the wave of the titanium trend. So just because a heater is made of titanium, doesn’t mean it’s high-quality.

No External Controllers

This one isn’t as critical, but the external controller is very misleading. It makes it seem like the heater is better than it is. All heaters have built-in controllers and temperature sensors. There is nothing special about them being separate from the heating element. Theoretically, a separate temperature sensor would keep the sensor from being influenced by the heating element, but in reality, this isn’t an issue. All-in-one heaters heat the tank just as well, so don’t think separate connected parts is something special or better.

Black Thermal Plastic

I prefer heaters that look good in the display. This has led me to use heaters made with black thermal plastic (often a casing around a metal body). My preferences are the Aqueon Pro and the Cobalt Neo-Therm. BulkReefSupply.com did a test to see how much variation a heater allows for before turning on and then turning off again and the Cobalt Neo-Therm had the most stable temperature of all the heaters they tested, only 0.05F! Other heaters allowed up to a 2-degree swing between the low where they kicked on and the high where they turned off.

The Winners

My top choice is the Cobalt Neo-Therm. They’re durable, look great, and are high-quality you can trust and rely on.

At about half the price though, I’m happy to use and recommend the Aqueon Pro which I’ve found to be about as good, except for the temperature range (which you can actually program directly in the controller anyway).


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