best aquarium heater

What is the best aquarium heater?

What is the best aquarium heater?

Selecting the right aquarium heater is a critical decision because if it malfunctions, it could spell disaster for your tank.

And those are just from Twitter…and it’s hard to rant on Twitter, given the character limitations with tweets.

So let’s dig into some of the things you want to think about before buying a new aquarium heater.

Selecting the best aquarium heater

Decision 1: Location, location, location

The first decision you need to make when shopping for the best aquarium heater is where you plan to install, place or locate it–because that will impact the design of the heater you select. There are two common designs to consider that will drive your decision in terms of what type you decide to buy:

  • In-line or external
  • Submersible

In-line aquarium heaters

Hydor in-line aquarium heater

In-line heaters (also sometimes described as external heaters), like the Hydor model shown here, are installed outside of the tank, most likely behind or below the aquarium–out of sight and out of mind. This is just my observation and opinion here, but I think of external heaters as being more likely to be used if you have a canister filter (an external filter where water is already being plumbed to and from) where it can easily be installed ‘in-line’.

Otherwise, the extra plumbing seems to be a bit of a hassle, and it requires a pump to drive the required flow of water.

What I like about this design is that:

  • You could literally put it anywhere, which is good if space or aesthetics are an issue
  • Pushing water through the heating element takes energy (from a pump) but

Submersible heaters

Submersible heaters, like the Aqueon Pro shown opposite on the page, are waterproof and are placed either inside the aquarium itself or in the sump area if you have one. From a Darwinian perspective, they appear to be winning the evolutionary race, because there are as many models of a submersible heater as there are species of beetles. Did you know there are 350,000 known species of beetles? Okay, there aren’t that many models of submersible aquarium heaters, but there are a lot

Generally speaking, there are two different designs for submersible heaters:

  • Glass
  • Titanium
Glass aquarium heaters

The most common type of submersible aquarium heaters has a heating element enclosed in a glass outer shell. To work properly, they need to be fully submerged under the water at all times. If they run for any appreciable amount of time outside of the water (or above the water line if there is evaporation), they will crack and malfunction.
I read accounts online of (inexpensive) glass heaters shattering when operating out of the water for even a few brief minutes. Yikes! You also have to be careful that you don’t bang them too hard into the aquarium wall or rocks, etc.

But don’t worry, some of the newer models have features that can help reduce this risk. When looking for a glass aquarium heater, look for a model with these features:

  • Made with shatterproof (or shatter-resistant) glass
  • Auto shut-off when out of the water (or if the water level dips too low)
  • Easy to set the temperature
Titanium (or aluminum)

The main alternative to the traditional glass submersible aquarium heater is the titanium heater. In a lot of ways, titanium could be considered to be the ultimate heating element for an aquarium, because it is lightweight, conducts heat well (and transfers that heat to the water efficiently…which is what you want), and it won’t rust in saltwater.

If you have a relatively large aquarium (I’m not judging!) about 75 gallons or larger, titanium may be your only option, if you want a heater in the ~300 watts or larger range. Which brings me to one of the next points: what size do you need?

Side note here, if you look closely, some models that look like a glass heater actually have an aluminum core, which is actually more effective at dissipating heat than aluminum, but due to the soft properties of aluminum (think about the foil in your kitchen), it tends to be covered in a protective plastic sleeve anyway.

The image here is the model I bought a few years back.

Which is better, glass or titanium?

Both heater designs will do their job and heat your water efficiently. From my perspective, I like the peace of mind knowing that a metal titanium heater won’t crack, break or explode. I also like the fact that most models have the thermostat/temperature setting far down the cord, which makes it easy to check and adjust the temperature, without getting your hands wet.

Decision 2: what size do you need?

Since the aquarium heater is responsible for warming up all the water in your tank and keeping it at a constant tropical temperature (usually ~78-82 degrees F), you want to make sure you have a large enough heating element to get the job done consistently.

An undersized unit will struggle to keep up when the house is cold. An oversized unit will run intermittently.

Here is the sweet spot, from my perspective:

  • >20-gallon tanks need less than 75 watts to heat the water consistently
  • 20-gallon tank needs a 75-100 watt heater
  • 29-gallon tank needs a 100-125 watts
  • 40-gallon tank needs 125-150 watts
  • 55-gallon requires 150-200 watts
  • 75-gallon needs 200-250 watts
  • Larger than that and you need ~300+ watts

best aquarium heater

Cover image credit of heater in the center: By Dr. David Midgley at en.wikipedia [CC BY-SA 2.5 (], via Wikimedia Commons

Decision 3: What features to look for in an aquarium:

  • Easy to control and set?
    • Most heaters (but not all) will allow you to adjust the setting–but not all heaters are easy to set or easy to read. A few years ago, when I had a bunch of tanks in my house running (that’s a separate story about addiction…), I had a few cheap heaters I was using to heat the rotifers, grow-out tubs (for fish fry), etc., and those heaters had an adjustable screw-type mechanism for setting the temperature. They weren’t impossible to read…but they weren’t the easiest things to read. Not the exact model but check out this one here–see what I mean?

glassEven if the dial is easy to set and read…where is it located? Will you have to reach your hand into the back bottom of the tank to adjust the temperature, or is the controller somewhere more convenient (like on the power cord) where you can adjust it easily. It seems a bit superficial, but you don’t want to buy another aquarium heater for a very long time, so why not take the time to think that part through and get the right features.

  • Auto-shut-off (air)–if you are in the market for a glass thermometer, consider buying a model with an automatic shutoff switch that turns the heater off when it is exposed to the air, this is an important safety feature to help prevent your heater from breaking (or exploding)
  • Auto-shut-off (overheating)–another important safety feature is an automatic shut off that kicks in if the heater starts to overheat. With this feature, you won’t hurt your corals and fish, even if the heater fails
  • Shatterproof -means the glass won’t go everywhere when it breaks, but this does not mean indestructible.

Reviews, reviews review

In this era of instant, digital information, it is important to look at the real-world experience of other aquarium owners. Take a look at the reviews on Amazon and other online retailers and try to read between the lines. The star ratings are a good place to start, but try to dive a bit deeper. What are the most common 1-star reviews about–did the titanium heater stop working after 8 months or are there reports of glass shattering?

Do they tend to run hotter or colder than indicated? or did more than one person complain it arrived dead in the box?

I do my best to provide helpful, accurate information here–but this is not the only source. Read those reviews, please.


The best aquarium heater for your tank might not be the exact same model that is right for someone else. Hopefully, after taking some of the factors from this article into consideration, you’ll feel better equipped to sort through and pick the best model for your situation and budget.






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