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If you own fish, it is important that they are kept in the proper environment. This is especially true if they are tropical. You want to invest in the best aquarium heater so that your fish thrive in the right temperature.

So, with all the different brands and models to contend with, how do you make heads or tails of them? That’s why we’re here. We put together this informational buyer’s guide to make your quest for the right heater much easier.

We narrowed down 10 entries that outperformed the rest and are sure to help you better care for your fish. But before we dive in, check out a couple of our favorite picks. We were impressed with what these brought to the table.

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First up is the Aqueon Pro. This aquarium heater is built to last thanks to its shatterproof body. It’s equipped with a handy electronic thermostat for easy temperature control. It is highly accurate and comes armed with safety features.

Then there is Cobalt Aquatics’ Neo-Therm. This attractive unit is much more than just looks. It sports an inconspicuous design that is easy to use while controlling a wide range of temperatures.

Top 10 Best Aquarium Heaters

We have plenty more options for you to choose from, each with its own unique benefits. Read on to see what’s in store, and don’t forget to stick around for the buyer’s guide afterward.

1. Aqueon Pro Review - Best Overall
  • Great warranty
  • Shatterproof
  • LED lights
  • Affordable
  • Takes a while to heat up
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Aqueon’s Pro gets our top pick as the best of the bunch. With its excellent performance and user-friendly approach, Aqueon delivers a solid contender. We like the even distribution of heat when it’s in action – exactly what you need for your fish.

We found the built-in electric thermostat to be very accurate. We like that it lets you adjust the temperature from a range of 68°F to 88°F. This gives you a nice margin, as tropical fish do best at around 78°F.

Another nice feature to see is the heater’s tough body. It’s built to be shatterproof, so it can withstand its fair share of bumps. And you don’t have to worry about its inner components getting damaged or malfunctioning.

The Aqueon Pro is also equipped with a safety shut-off feature in the event that it overheats. And for easy management, onboard LED lights let you know when the heater is active and when optimal temperature has been reached.

Best of all, this heater is affordable. You don’t have to break the bank to get reliable heat for your fish. A lifetime warranty is even included with its low cost.


  • 1.5 x 1.8 x 12.8 inches
  • Lifetime warranty
  • 13 ounces
  • 200-watt

Ease of Use

A simple dial with an LED light is all that’s used to adjust the temperature. Built-in safety features take care of the rest to let you know when the heater is running.

2. Cobalt Aquatics Neo-Therm Review - Best Design
  • Good warranty
  • Easy to use
  • Nice design
  • Built tough
  • Emits a bad odor
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More so resembling a vacuum attachment, Cobalt Aquatics’ Neo-Therm sports a unique design you don’t often see on aquarium heaters. It has a very thin profile compared to others. But that doesn’t make it any less of a performer.

In fact, the Neo-Therm impressed us quite a bit with its easy temperature settings and tough design. We like that you can place this just about anywhere due to its thinness.

This one is very user-friendly. It is equipped with a straightforward, one-touch feature for setting the temperature you want. It lets you select from a range of 66°F to 96°F. Once the desired temperature is met, a built-in LED light activates to let you know.

Cobalt Aquatics made the Neo-Therm heater with thermoplastic and resin. This ensures that it is shatterproof and nearly unbreakable. You also get a nice 3-year warranty in case you have any troubles out of the heater.


  • Thermoplastic and resin
  • 3.2 x 2.2 x 7.8 inches
  • 3-year warranty
  • 10.9 ounces
  • 50-watt

Ease of Use

Simply press a button to set the temperature you want. An onboard LED dial lights up and cycles through each degree setting. Once you have it at the temperature you want, the unit heats up until reaching your selection.

3. Tetra HT20 Review - Easiest to Use
  • Great for small aquariums
  • Very easy to use
  • Affordable
  • Compact
  • Can’t adjust temperature
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If you’re not looking to spend a whole lot but need to heat up your aquarium, Tetra has the perfect solution. Their HT20 heater is a breeze to use and comes in a nice little compact body. It is fully submersible, helping to heat up your water faster.

This one is better suited for smaller aquariums, so you don’t want to try it on anything over 30 gallons. We like that there isn’t anything to fuss with here. The Tetra HT is built to automatically heat up your water to 78°F. You don’t have to make any adjustments; just drop it in place and turn it on.

A suction cup lets you mount it just about anywhere you see fit. Since it takes up so little space and is quite small, it blends into most aquariums nicely.


  • 5.2 x 1.6 x 3.5 inches
  • LED indicator
  • 6.4 ounces
  • 100-watt

Ease of Use

A simple LED light tells you everything you need to know. When the Tetra HT is heating up, the light is red. Once the optimal temperature is reached, the light turns green. If you are looking for something easy, this is the one for you.

4. Hydor In-Line External Heater Review - Best In-Line Heater
  • Even temperatures
  • Fast installation
  • Easy to use
  • Nice design
  • Can only be mounted vertically
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This external aquarium heater from Hydor works to heat up the water before it goes into your aquarium. This is a great way to free up valuable space inside your tank. It’s a cinch to install and begins working immediately. The only caveat with this unit is that it can only be mounted vertically.

You can use the Hydor In-line with either freshwater or saltwater fish. We like that it is equipped with safety shut-off features in the event that there’s a malfunction. So instead of your aquarium water overheating, the heater simply shuts itself off.

Operation is really straightforward on this model. It’s also really effective. We loved how easy it was to get set up and running. It’s a little costly compared to some of the previous units we looked at. But for many fish owners, the high level of quality is well worth it.


  • Positive Thermal Coefficient element
  • 4 x 4 x 12.5 inches
  • 300-watt
  • 1 pound

Ease of Use

Setting your desired temperature is a piece of cake. A simple built-in dial lets you make your selection. The Hydor In-line provides a range of 64°F to 93°F.

An onboard LED light indicator lets you know when the heater is running at your selected temperature.

5. Marineland Precision Heater Review - Best Value
  • Nice, even heating
  • Dial is easy to use
  • Durable design
  • Easy to install
  • Quality control issues
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Marineland’s Precision Heater boasts a numerical dial and a visible temperature display. We like the thin profile of this one. It doesn’t take up much aquarium space and is easy to mount.

The mounting brackets sport windows so you can keep an eye on your heater’s temperature. The dial on top of the heater has clear degrees shown so you know exactly what temperature you’re selecting.

We tested the 200-watt model from Marineland, which easily accommodated our 50-gallon tank. They provide many other models for various aquarium sizes if you require something different. It’s hard to beat the price that they are offering this one at, making it a fantastic bargain.

The only issue we had was that this heater isn’t well insulated. We found that other users had the same problem. It appears to be a quality control issue, as our replacement worked flawlessly.

And that deserves some praise, too. If you do receive a defective unit, a working replacement will be sent to you promptly.


  • 3.9 x 1.6 x 14.8 inches
  • Safety shut-off
  • 10.4 ounces
  • 200-watt

Ease of Use

Mounting the Marineland heater is rather straightforward. And we found using it to be a breeze. We like the clicky dial on this one. It increases or decreases the temperature in single-degree increments.

6. Eheim Jager Aquarium Heater Review - Best for Small Tanks
  • Nice temperature dial
  • Great build-quality
  • Well-priced
  • Precise
  • Poor customer service
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We really like Eheim’s Jager due to its precise temperature distribution and user-friendliness. You can use the Jager in either marine or freshwater tanks. If you’ve been in the market for a heater that can take a beating and will last, look no further.

Eheim used shatterproof glass that features shock resistance. You won’t have to worry about this one getting bumped or broken. It feels great and is lightweight, too. We like that you can easily adjust the temperature using the built-in dial.

There are safety features in place that will kick the unit off in the event that it overheats or is exposed to a dry environment. It also shuts off if your aquarium’s water level gets too low.


  • 1.4 x 19.9 inches
  • LED indicator
  • 13.1 ounces
  • 300-watt

Ease of Use

You get quite a broad range to choose your desired temperature, from 65°F to 93°F. A dial at the top of the unit adjusts the temperature with ease.

We had no troubles with this one, as each increment clicks when you turn it. We found that it’s easily one of the best heaters around for smaller aquariums.

7. Fluval E Electronic Heater Review - Best Display
  • Accurate reading
  • Nice display
  • High-quality
  • Easy to use
  • Must be mounted at a 45° angle
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Fluval kicks things up a notch by delivering a heater with a built-in LCD screen. This display shows you the heater’s current temperature level. This way you always know how the water in your aquarium is doing.

It’s built with two temperature sensors to provide you with the most accurate reading possible. We really like how the LCD screen changes color as it cycles through its phases. It will begin flashing if there is a problem, letting you know if action needs to be taken.

We love how easy this one is to adjust. It’s also built tough to prevent damage from fish or other outside sources. Fluval really went the extra mile here to deliver an aquarium heater that makes use of technology in a convenient way.


  • Adjustable temperature
  • 1.8 x 3.3 x 18.2 inches
  • VueTech LCD screen
  • 1.05 pounds
  • 300-watt

Ease of Use

You can adjust the heater’s temperature anywhere from 68°F to 93°F. Mounting brackets are included that make installation a cinch.

We like that once it’s mounted, you can remove the heater without removing the brackets. It’s a very user-friendly design that serves the user well.

8. Zacro 50W Review - Most Budget-Friendly
  • Great for small tanks
  • Accurate reading
  • Affordable
  • Only heats small aquariums
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Are you on a tight budget? Do you need to heat up a small aquarium? Then Zacro has exactly what you need. Their 50-watt electric heater comes at a very affordable price and gets the job done well.

This heater is completely submersible and totally waterproof. Zacro used double-sealed plastic that works to protect the inner components while keeping your fish safe. You can see the heater’s current temperature at all times thanks to a built-in analog readout.

You don’t want to use Zacro’s heater in an aquarium larger than 16 gallons. You will be sorely disappointed with the outcome. But for smaller tanks – as it was intended – this one works like a charm and won’t let you down.


  • Double-sealed plastic
  • Waterproof
  • 8 ounces
  • 50-watt

Ease of Use

This one is a breeze to install. You can easily change the heater’s temperature from a range of 65°F to 93°F.

The built-in display makes it easy to keep an eye on the current temperature so you know if adjustments need to be made.

9. Aquatop GH-50W Review - Most User-Friendly
  • Nice temperature range
  • Good for beginners
  • Easy to use
  • Occasional fluctuations
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Aquatop delivers another fine entry for heating smaller aquariums. This model is best suited for units that are no larger than 13 gallons. You won’t find a lot of fancy bells and whistles here. It sports a very basic design, but it works well enough.

A small knob at the top of the unit changes increments either in the positive or negative. You have to look down to the side of the heater to see your temperature selection. But considering its low price, this is only a minor inconvenience.

We found that Aquatop’s unit heats up well. It gets the job done without much fuss. The unit we looked at was Aquatop’s 50-watt model, but they offer ones that go all the way up to 300. So if you need a heater for a larger aquarium, they have you covered.

For the price and performance, we can’t recommend this one enough. It works well and gives you a nice temperature range to work with. The heater is suitable to use in either saltwater or freshwater aquariums.

It is well-built and features double-insulated glass to protect the inner heating element. An onboard LED light lets you know when your selected temperature has been reached for easy monitoring.

If you’re new to owning fish and want a basic heater that won’t overwhelm you with a bunch of settings, you’ll like the GH-50W. The temperature does fluctuate on occasion, but nothing of concern.


  • Heats up to 13 gallons
  • 9 x 1.5 x 1.5 inches
  • 9.6 ounces
  • 50-watt

Ease of Use

Simply turn a small knob to set the heater to your desired temperature. An analog display shows you the heater’s current temperature. It’s all very straightforward and quite easy to operate. You can choose from any temperature between 65°F to 93°F.

10. Aqueon 300-Watt Heater Review - Best for Big Tanks
  • Great for large aquariums
  • Easy operation
  • Durable
  • Very basic design
  • No temperature readout
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If you want a heater for your large aquarium that performs well, Aqueon delivers the goods. This thin unit won’t take up much room, leaving more space for your fish to thrive. It features accurate temperature distribution within one degree.

Another big plus is its construction. Aqueon used shatterproof plastics to ensure that you’ll get plenty of use out of their heater. There’s even built-in safety protocols that kick off the unit in case there is a malfunction.

So you never have to worry about your fish when you leave the house. The unit will never overheat or harm your fish, either. While this is a really basic model, it is lacking an important feature that we really missed having handy.

You won’t find a temperature readout. You can only go by the selection you make with the onboard dial. A small LED light lets you know when it has reached your desired temperature, but that’s about it. You basically have to take the heater’s word for it, so to speak.


  • 1.31 x 1.31 x 15.13 inches
  • Automatic shut-off
  • Shatterproof
  • 10 ounces

Ease of Use

You can choose any temperature between 68°F and 88°F for the heater to set itself to. The dial used for this is easy enough to use, although you can’t monitor changes in temperature.

Buyer’s Guide to the Best Aquarium Heaters

Now that you have seen our highest-ranking aquarium heaters, we want to switch gears a bit. In this buyer’s guide, we want to help you get a better understanding of what you need to watch for when shopping for the right heater.

There are important factors that need to be considered before you stick any old heater into your aquarium. We want to make doubly sure that you get the proper unit for the needs of you and your fish.

Types of Aquarium Heaters

There are 3 main types of heaters you want to look for. Some are more expensive than others. But what matters most is how well it serves your needs, heats your aquarium, and benefits your fish.


Usually tube-shaped, these cylindrical heaters are powered by electricity. They only go partially inside your aquarium’s water. They are often made of durable plastic or glass. Some feature digital displays, while others use an analog dial for manual temperature adjustment.


These are a good idea if you have four-legged pets that could possibly come into contact with your aquarium’s heater. These types of heaters go all the way into the water where they are out of the reach of children and pets.

Some fish owners feel that these types distribute heat better throughout the aquarium. The nice thing about these is that you can place them just about anywhere you see fit. Just remember to mount them away from any plants you may have in your aquarium.

If they come in contact with each other, you risk damaging or ruining the heater. This could also cause life-threatening injury to your fish. It is vitally important to their well-being that you remember to keep the heater and plant-life away from one another.


This type of heater attaches to your filter’s line, hence the name “in-line”. Many fish owners who have large aquariums prefer in-line heaters because they don’t take up valuable space inside the tank.

Location placement depends on where your filtration system is located. The in-line heater is generally installed somewhere between it and the aquarium.

Choosing the Right Wattage

It is important that you use a heater that is suited to the size of your aquarium. So, how do you know which works best? You can usually find this information with the heater. But just in case it isn’t listed, here is a handy chart.

It’s a good idea to study this so that you know exactly which heater will work for your needs. Knowing this will help to speed up your search exponentially.

  • If you have a small 5- to 10-gallon aquarium, you want a heater that ranges anywhere between 25 and 75 watts.
  • If your aquarium is medium-sized at around 20 to 25 gallons, you can get away with a heater that’s between 50 and 200 watts.
  • For large aquariums that hold around 40 to 50 gallons of water, you’ll need a heater with anything from 100 to 400 watts.
  • And for even larger aquariums that hold 65 to 75 gallons, you want a heater that’s capable of 200 to 600 watts.

Now you can safely choose the best heater for your aquarium. Remember, the type of heater you decide on is largely based on your preferences. But its wattage has to sufficiently heat the capacity of your aquarium.


Where Should I Mount My Aquarium Heater?

Good question. This depends on the type of heater you have. If you’re dealing with an immersion heater, try to get it as close to your aquarium’s filter outlet as you can. This will ensure that water is heated evenly as it gets dispersed into the aquarium.

Since part of these heaters protrude out of the tank, you want to make sure that children and pets are unable to reach them. If at all possible, place them near the back of the tank where they are out of reach.

If you have a submersion heater, you can pretty much place it anywhere in your tank that gives it the best heat distribution. Just make sure that you avoid any plant-life you might have. You will likely get the best results, however, if you mount it near the middle of your aquarium.

If you’re using an in-line heater, mounting is a bit different. Since it has to be attached to your filter line, you are a bit limited in where you can put it.

Can I Use Two Small Heaters Instead of a Large One?

Absolutely. In fact, many fish owners prefer to do this, as it more evenly distributes heat throughout the aquarium. If you decide to go with this method, just make sure that each heater is of equal distance apart from one another.

This will ensure that your water gets the best heat distribution. If you have them right next to each other, you will defeat the purpose of using this method of heating. You would be better off using a single large heater.

How Often Should I Turn Off the Heater?

Ideally, never. Once you have it properly installed, you want it to run all day, every day. The heater will do all the work for you, assuming it is working correctly.

Now, obviously you’ll want to turn it off whenever you change your aquarium’s water. But aside from that, leave your heater running at all times.