6 Best Aquarium Heaters to Ensure Your Fish Thrive

There are places in the world where they keep tropical fish without worrying about heating the water. Such places are called ‘the tropics’.

The rest of us need to choose an aquarium heater that will keep tank water in the range preferred by our fish: usually between 20-30 ºC, with 24ºC being suitable for most common tropical fish.

Note that even if you heat your house, an aquarium heater is usually required. That’s because the aquarium water doesn’t just need to be warm, the temperature should also be as stable as possible.

In the cases where you don’t consider the temperature of the aquarium water, this can lead to so many problems including stress and health-related issues, fatalities, and all other aspects of your tank will be affected, including your plant life. However, while this is such an important point to think about, the solution is simple. Invest in an aquarium heater.

By buying and installing a heater, you can effortlessly regulate the temperature of the water in your tank and completely avoid any of the temperature-related issues we’ve listed above.

Best Aquarium Heaters

Whether you’re buying a heater for the first time, or you simply looking for a great heater to replace or upgrade your existing one, we’re here to help. We’ve searched across the market at what’s out there and narrowed down the best to just the best of the best.

1. Fluval E 100-Watt Electronic Heater

Fluval E100 Advanced Electronic Heater, 100-Watt Heater for Aquariums up to 30 Gal., A772
  • Comes with a premium 5-year warranty
  • Color-coded LED screen to show if the temperature is suitable
  • Fast-Heat feature with auto safety shut-off
  • Protective casing to stop aquarium life from becoming burnt
  • Temperature can fluctuate a couple of degrees

Starting off our list, we’ve chosen the Fluval Electronic Heater, easily one of the most popular aquarium heaters available on today’s market, and for a good reason. This particular line balances quality, performance, and price, making it an all-around great heater for any tank or basic temperature control purposes.

While this particular model is 100-watt, if you’re looking for more power, there are both 200 and 300-watt versions available. However, what we really love about this heater is the built-in color-coded LED display. This shows the temperature in both Celsius and Fahrenheit and comes with a leading range of 68-93°F.

What’s more, you can trust this heater is accurate thanks to the dual sensor technology which always provides you with the real-time temperature at a glance. Furthermore, in the case that you’re changing the water, there’s even a quick heat function with an auto safety shut-off feature to ensure the water is always perfect.

Despite having all these features, the Fluval heater is incredibly easy to use and built to protect your fish from burning themselves thanks to the simple casing. In short, there’s really nothing bad to say about this heater that guarantees to get the job done!

2. Tetra HT Submersible Aquarium Heater With Electronic Thermostat

Tetra HT Submersible Aquarium Heater With Electronic Thermostat, 50-Watt
  • Available in 50 and 100-watt varieties
  • Heating operational indicator light (red/green)
  • One of the most affordable aquarium heaters available
  • Completely waterproof design
  • Doesn’t last as long as other heaters on the market

If you’re looking for a super-affordable option for an aquarium heater, but you still want access to a quality product that’s built to last, the Tetra heater, another household name in the world of fish tanks, could be the perfect option for you.

This heater is designed with smaller tanks in mind, usually around the 35-gallon or less mark. There are both 50-watt and 100-watt versions available, allowing you to choose the one that’s right for you. Both come with all the features you’ll need to heat your tank accurately.

Most importantly, there’s an electric thermostat built right into the heater, so you won’t have to worry about buying it separately, and for the most part, this heater can be automated to stay on a certain temperature range.

There’s also an indicator available, so you can check whether the heater’s on, which is indicated using a red light, and green when the water is at the desired temperature. What’s more, this heater can be fully submerged into your tank without the worry of water damage.

In short, this is one of the most popular fish tank heaters out there. The heater has a long lifespan, has a ton of features to use that can give you a great experience, and for such an affordable price tag, what more could you ask for?

3. Aqueon Pro Adjustable Heater (200-Watt)

Aqueon Adjustable Pro Aquarium Heater, 200W
  • Comes with a limited lifetime warranty
  • Perfect for all aquariums under 35 gallons
  • Adjustable temperature readings and settings
  • Virtually destructible design
  • A bit more expensive than other heaters on this list

The final aquarium heater we’ve chosen to list here today comes from Aquaeon. If you’ve been in the aquarium world for some time, there’s no chance you won’t have heard of this game-changing brand. Renowned for its quality products, this pro heater is everything you’ll need.

Firstly, while this is the 200-watt version, there are plenty of options available ranging from 50 watts to 250 watts, which is ideal for all aquariums around the 35-gallon mark and under. Built into each heater, you’ll be able to adjust the overall water temperature anywhere between 68°F and 88°F.

Perhaps the best feature that everybody loves this heater for, however, is the fact that it’s basically indestructible. The heater itself is designed and crafted using shatterproof glass, and it’s completely submersible, so you can put it below the water line without fear of it breaking.

With a limited lifetime warranty to back this up, this could even be the last aquarium heater you ever need to buy!

4. Eheim Jager Aquarium Thermostat Heater

EHEIM Jager Aquarium Thermostat Heater 100W ( Pack of 1)
  • Made from anti-shatter glass for a highly durable build
  • TruTemp technology for accurate temperature setting
  • Built-in thermostat for monitoring the water temperature
  • Automatically shuts off when it detects a lack of water
  • A more expensive option than your typical heater

Whether you own a single tank that you want a heater for, or you own multiple tanks of different sizes, sometimes you need a selection of heaters, so you can find the perfect one for you. With these awesome and affordable heaters, you’ll be able to choose from any wattage ranging from 25 watts, all the way up to 300 watts, ensuring you’ll be able to find the perfect one that fits your tank. But don’t worry, while there are a lot of choices here, there’s no compromise on functionality.

This heater is fully submersible, allowing it to heat your water thoroughly and quickly, and has a range of built-in features such as the heater turning off automatically when the water level is too low, perfect for if you’re cleaning, or taking the heater out for any reason, and a numbered dial for easily setting an accurate temperature.

What’s more, this heater is highly accurate thanks to the built-in thermostat and integrated TruTemp dial that helps to keep the temperature balanced and consistent; although there’s no screen for displaying the exact reading.

This is easily one of the best aquarium heaters out there. It’s very easy to use, and you’ll be familiar with it in just a matter of minutes. While this is a bit more expensive than your typical heater, its functionality of it is completely worth it.

5. Hygger Submersible Aquarium Fish Tank Heater

hygger 100W Mini Submersible Digital Display Aquarium Heater for Small Fish Tank, Compact and Fast Heating Thermostat, with External Controller and Built-in Thermometer, for Betta, Turtle
  • A great customer service team
  • A fantastic range of temperatures
  • Internal thermometer with an auto-shutoff feature
  • Clear LED display for seeing all information
  • None!

Hygger is another awesome brand that produces a high-quality line of aquarium products, including powerful and durable heaters that are renowned for their performance and reliability. This fully-submersible version is no exception to the rule.

As the title suggests, you can fully position this heater in your aquarium, ensuring you’re able to get the best position that’s right for you. Even once submerged, there’s a built-in thermometer, complete with an auto-shutoff feature to stop your water from overheating, and a dial on the power lead so you can easily set the temperature to whatever you want it to be.

This amount of temperature control ranges from around 68°F to 93°F, which is more than enough for any kind of fish in your tank. Of course, being a premium quality heater, this one comes with a clear LED display that helps you see what the accurate temperature is, adjust the settings, and indicates when the heater is on and working.

Installation is also effortless thanks to the two included suction cups, and there’s even an added plastic heater guard that stops your fish from going up to the heater and hurting themselves.

With a great customer support team, a high-quality heater, and all for a good price, this is one aquarium heater where you can’t really go wrong!

6. Cobalt Aquatics Neo-Therm Aquarium Heater

Cobalt Aquatics Neo-Therm Pro Aquarium Heater (50 watt) - Dual Display, Fully-Submersible, Shatterproof Design, Black, 50w (up to 12 gal)
  • Crafted from shatterproof materials
  • Comes with a 3-year warranty
  • An incredibly helpful LED color-coded temperature display
  • Comes with integrated suction cups for easy installation
  • None

The final aquarium we’ve chosen for our ‘best of’ list is a true high-performance piece of equipment. If you’re in need of a highly functional heater that goes the extra mile and provides you with the best experience, there will be no reason to look further than this range.

The Cobalt Aquatics’ leading feature is the awesome LED light circle that displays the current temperature of your tank’s water. This display is super easy to use (yellow means the water is too cold, green is just right, and red is too hot), and each integer is labeled in Fahrenheit for a precise reading at a glance.

You can then use the dial at the top to select which temperature you want in the simplest way possible. The body of the heater is made from shatterproof materials, which is then complemented by a 3-year warranty, giving you complete peace of mind that this is a heater that’s built to last.

If you’re on the hunt for the best heating experience, it doesn’t get much better than this. The heater works perfectly every time and remains consistent while you’re using it. There are no fluctuating temperatures here; a common problem with some of the cheaper aquarium heaters.

With instructions on how to use and set it up, suction cups for attaching it to your tank, and all the features you’d expect in a premium quality aquarium heater, there’s no reason you’d need to hesitate with this fantastic heater.

Choosing The Best Tank Heater for Your Needs

Fish, particularly more delicate ones like marines and discus, are as stressed by fluctuating temperatures as they are by water that’s too warm or cold. You don’t want the temperature to dip at night and then rise by day, for instance.

Aquarium heaters must therefore use thermostats to keep the temperature constant. The thermostat may be a separate device that you connect to the heater or, far more commonly these days, it can be built into a single device with the heater.

What size aquarium heater?

Aquarium heaters are rated in watts. Manufacturers also state on the packaging what size tank a particular heater is designed for.

The rule of thumb is that you require five watts per gallon to heat one gallon of water. So a 20-gallon tank would require a 100-watt heater.

The five watts per gallon rule is pretty conservative, especially with large tanks in centrally-heated homes. (Larger tanks lose heat more slowly than smaller tanks). If you have a 30 or even a 40-gallon tank, unless your house gets very cold at night you’ll find a 100-watt heater will suffice.

For larger aquariums it’s better to have two heaters, and to split the wattage. So for a 50-gallon tank, you might have two 100-watt heaters, say. The reason is that if the thermostat fails and the heater sticks ‘on’, you hopefully won’t boil all your fish before you notice a heater is broken. (I’ve over-heated a small tank of fish, and it is a dispiriting experience indeed).

Some new heaters include an alarm to warn you when they stick ‘on’, or you might notice from strange fish activity such as gasping at the surface, or from the thermometer of course. If your heater does fail, turn it off but don’t remove it right away as the glass can get very hot and may crack over your fish tank.

Types of aquarium heater

There are several types of aquarium heater, although nearly everyone now uses the standard combined heater/thermostat units, which are cheap, fairly accurate and very convenient. I’ll consider some more specialized heaters below, too.

Combined heater/thermostat

These are long thin glass tubes, containing the heater at the bottom and the adjustable thermostat at the top. The whole unit is designed to be submersed in your aquarium. The unit can crack if it’s switched on without water, and it can also get too hot to touch, so take care when cleaning your tank – even though you’ve switched the power off first.

The heater is always a coiled element within the tube, though some modern units make the tube out of toughened plastic rather than glass. Tough plastic is less prone to cracking or burning aquarium inhabitants.

The thermostat may be an old-fashioned metallic strip element or a more modern microchip-based unit. The former have stood the test of time, though the latter may be more accurate – at least until the chip fails! If a microchip thermostat should fail, the chip is meant to fail in the ‘off’ position, giving you plenty of time to install a spare heater when you notice the tank cooling. Warming water quickly is a much more dangerous situation.

Combined units invariably have a light at the top to tell you when the heater is working. Position the unit so you can see this light when the heater is on, so you can check things are working as they should. (e.g. If the tank is too cool, the light should be on to show the heater is working).

Combined heater/thermostats are the best choices for 95% of aquariums.

Separate thermostat

Sometimes you may want to heat your tank the old-fashioned way, using a separate heater and a thermostat. For instance, you may be using an under-tank heater or you might want to use a smaller heater in your aquarium, keeping the bulky thermostat outside of the tank.

External thermostats are easier to adjust, and your hands can stay dry. The combined cost will be more expensive though.

Undertank heater mat

These became quite popular in the 1990s, but I don’t recommend them. The theory is great: you place your tank on a heater mat, which warms the tank through the glass. The temperature is controlled via a separate thermostat. An ugly thing is removed from your fish tank.

Unfortunately, glass is a bad conductor of heat, and gravel on the bottom of the tank doesn’t help with circulation at all. This can make using these units rather erratic. Worse, if the heater fails you’ll need to drain and move your tank to replace the heater.

Best left for keepers of tropical reptiles and amphibians, in my view.

Heating cable

These don’t replace normal heaters, but rather are an addition to help grow plants. They are thin cables that you snake through the aquarium gravel. They are usually fixed in place with suckers before the substrate is put on top.

The idea is that the gentle local heating promotes water movement through the aquarium gravel, stimulating the roots of plants just like springs in nature, and helping with fertilization.

Heating cables were very popular a decade or two ago with planted systems from the likes of Dernelle and Dupla. However many modern aquascapers (including the Japanese planted tank master Amano) don’t use them.

Heater cables may be worth experimenting with if you’ve got several tanks, but expensive and certainly not essential for plant growth.

In-line heater

If you use an external filter, you can buy heaters from manufacturers like Hydor that you plumb into the tubing between your external filter and your tank. As water runs through the heater it’s warmed up, which provided you use a sufficiently powerful filter pump can be an efficient way of heating the tank.

The external casing of an in-line heater is usually made of heatproof plastic, so it’s safe to hold, and won’t start fires. But the bigger advantage is that you’ve got the heater out of the aquarium, which could be good if you’re aquascaping or keeping fish that could burn themselves (some big catfish or seahorses, for example) or that will even fight with equipment (certain cichlids in freshwater tanks, and triggers in marine tanks).

In-line heaters are quite new, however, and more expensive than normal units. There’s also a danger with anything plumped in-line that it can come unplumbed. Every extra cut in the tubing is another opportunity for leaks.

External heater/filter (thermofilter)

Some external filters combined filtration with heating in the same bit of kit. Water passing through the filter is also heated, with the temperature controlled by settings built on top of the filter canister.

The advantage of these units is no extra plumbing and no danger of the leaks we just mentioned. Disadvantages include the cost – more than the equivalent filter plus even an in-line heater, let alone a conventional heater/thermostat – plus the fact that if the heater fails you’ll have to discard the whole device.

The most popular make, the Ehiem Thermofilters, has a good reputation for reliability, but everything man-made will fail someday. Also note that if you keep marines, make extra sure the heater/filter is suitable for saltwater use. Some aren’t.

Other things you’ll need when heating an aquarium

A thermometer: This is essential, to enable you to monitor the tank temperature and to look out for heater failures.

Spare heater: Always have at least one spare heater in the house, in case yours fails. Even if you live minutes from the local fish store, you can bet your heater will fail on a Sunday, or at midnight when it’s closed.

A heater guard: These are cheap plastic guards that fit over the heating element of a conventional heater. They are said not to affect its performance, and they will stop some fish burning themselves on a very hot unit. I’ve used them in seahorse tanks since seahorses will wrap their tails around anything they can. May be worth the small amount of money they cost.


As you can see, when it comes to choosing the right heater for your aquarium, there are plenty of different options out there to suit what functionality you’re looking for and your desired price tag. Any of the eight heaters we’ve listed above make perfect choices, and you’ll be well on your way to owning the aquarium you’ve been dreaming of.


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