The 5 Best Aquarium Heaters – Reviews and Ratings

Unless your home stays at the exact temperature that’s best for your fish, you’ll want your aquarium water to stay in the optimal range for your fish’s native habitat. Fish are ectothermic, which means they rely on their environment to provide the heat their bodies need. 

While there are severe health effects from water that is too warm, of course, there are also negative health effects from water that is too cool.

Cold water can cause stress and illness for a fish and vastly reduce their lifespan. 

Even as an endothermic animal, I experience this every time I forget to turn on the thermostat during a cold snap!

Before I know it, I’m curled up in bed without regard to my to-do list. Over time, my body gets tired and I get sick. With fish, it’s kind of the same thing.

The best aquarium heater will keep your fish at the right temperature, reducing their chance of developing illness or parasitic infections.

Even better, some fish are at their brightest and most beautiful at their optimal temperature. 

Let’s find out what kind of fish tank heaters will serve each individual tank the best.

Best Aquarium Heater Quick-Find Table

Image Product
  • Submersible
  • 300w to 800w
  • Best for saltwater tanks
  • Submersible
  • 300w to 800w
  • Best for saltwater tanks
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  • Submersible
  • 25w to 300w
  • Best for small fish tanks
  • Submersible
  • 25w to 300w
  • Best for small fish tanks
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  • Submersible
  • 100w to 300w
  • Best with a display
  • Submersible
  • 100w to 300w
  • Best with a display
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  • In-line
  • 200w to 300w
  • Best for external heating
  • In-line
  • 200w to 300w
  • Best for external heating
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  • Submersible
  • 50w to 300w
  • Best budget option
  • Submersible
  • 50w to 300w
  • Best budget option
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Types of Heaters

Hanging and Submersible Heaters

These are the most common types of heaters you’ll find in any store.

They look very similar, so you’ll need to fully examine the description. A hanging heater cannot be fully submersed and will likely fail if it is submersed. 

A submersible heater can be fully submerged – diagonally, horizontally, vertically.

They can fit right into your fish tank’s water flow to efficiently heat, and for something that will be placed into water, it can handle it. These filters require more attention to water changes as they can be damaged by being run dry or changes without allowing them to acclimate first.

Fully submersible heaters should always come with suction cups to attach the heater to the aquarium wall.

Note that any time you introduce something to your tank, your fish may get curious and get into it.

A heater directly inside your tank may invite a curious fish to investigate. Less careful fish may burn themselves on it.

If you have detective fish that want to get into your heaters, you can consider a different type of heater, such as a sump heater, or simply a style with a caging to keep your fish from touching the heater directly.

In this article, we’ll primarily cover fully submersible heaters.

They may not be the right pick for everyone, but they are the perfect choice for most situations. Not only are they practical, but they are reliable, and you can depend on them running accurately for much longer than other varieties of heaters.

Sump heater

Sump heaters are simply heaters kept in the sump.

It’s a valid heating option if it keeps your water where you want it but do exercise caution if your sump is acrylic.

Acrylic tanks and titanium heaters are especially a cause for concern as the titanium can melt them. 

In-line & In-Filter Heaters

Another common option, an in-line heater connects to the line from a canister filter into your tank, while an in-filter heater will be found inside a canister filter.

Both heaters are serving the same purpose of heating water while it runs through the filter and returning water at the optimal temperature. 

Substrate Heater

A substrate heater is usually a cord with a thermostat that lines the substrate in your fish tank.

These are absolutely the best for plants.

They aren’t designed as much with fish in mind as live plants, with their roots in soil which may not heat as well as the water above it. They encourage plant growth and absorption of essential nutrients.

These heaters are not the best choice if you are looking to heat your fish, as they aren’t as exposed to water current to move the heat they produce, and the sensor doesn’t monitor the water. 

Reviews of the Best Aquarium Heaters

After a ton of research and testing, here are our top 5 favorite aquarium heaters that get the job done at a reasonable price point.

We also cover a couple popular options that we feel aren’t high quality enough to make the cut, so be wary of buying things just because they have a lot of Amazon reviews…some of the top companies of the past have seen manufacturing standards slip!

Our top choice for pretty much all aquariums between 40 and 265 gallons, this is a workhorse and should heat up any aquarium enough to keep your fish happy and healthy.

Finnex-Deluxe-Titanium-Heating-Tube

The Finnex Deluxe Titanium Heater is our top pick. It can handle up to 265 gallons with a single heater while working perfectly well for as little as 40 gallons!

This is a fantastic choice if you have a larger tank, want a little more heating power, or even just a more durable and reliable option. If you’ve needed to throw out a heater before due to a thermostat issue – or worse, seen the consequences of a bad thermostat, you will be happy to know you can use your own thermostat to manage temperature. 

This durable heater doesn’t limit itself to saltwater and will be at home in a freshwater tank as well.

What We Liked About This Product

  • Heats up to 265 gallons
  • Corrosion resistant; great for saltwater tanks
  • Low cost
  • Separate thermostat
  • Heater cage
  • Keeps up with high temperature species
  • Reliable

Why It Might Not Work for You

  • No included thermostat; must buy a separate controller
  • Not good for small tanks
  • Shouldn’t be used with acrylic

Our verdict: 5/5 stars. Buy it.

If you’ve got a 40-265-gallon glass tank and you’re willing to buy a controller, this is a fantastic choice.

Even with the cost of a controller, it’s hard to find something this well built in this price range. As far as adjustability goes, it’s hard to get a more adjustable fish tank heater than one with an external controller that could even be set up to include a fan to run when it gets too warm.

>> Tap Here to Read More Reviews and See Today’s Price on Amazon.com <<

BEST WITH INTERNAL THERMOSTAT

#2. Cobalt Aquatics Neo-Therm

Cobalt Aquatics Flat Neo-Therm Heater with Adjustable Thermostat

Cobalt has designed a unique product you would recognize anywhere. It’s a sleek, good looking heater that won’t detract from your tank’s aesthetic. It can heat a tank up to 96 degrees whether you have a Nano-sized 6-gallon tank or a large-sized 140-gallon tank.

As far as small aquarium heaters go, you may even notice these running in tanks as small as a gallon or less for shrimp displays in fish stores. With their entire body being wrapped in a protective covering, even curious Neocaridina shrimp are safe to investigate this heater!

Of course, this small size and great coverage means this it is also the best heater for bettas, who will need much smaller, individual tanks. 

The NEO-therm, best of all, carries a reputation for reliability and longevity. 

 What We Liked About This Product

  • Attractive design
  • A quality heater for small tanks (a rarity)
  • Heavy duty cage
  • 3-year warranty
  • Takes up very little space
  • Easy, visible temperature dial

Why It Might Not Work for You

  • Expensive
  • Included thermostat is more likely to not shut off than not turn on
  • Easy to bump the dial

Our Verdict: 4/5 stars. Buy it.

Cobalt truly is selling a great product. It’s innovative, comes with a 3-year warranty, and is easy to operate. 

You’ll want to avoid older and used options, as an earlier generation had a habit of spewing black goo.

In general, you’ll be hard pressed to find a higher quality, better designed heater than the NEO-therm.

>> Tap Here to Read More Reviews and See Today’s Price on Amazon.com <<

Fluval Advance Electronic Aquarium Heater

The Fluval E is popular for its genius design with a big, colorful display for its temperature. Not only does the thermostat tell you what temperature it’s set to and what it is, but it does something many other heaters don’t: It tells you how it’s doing. It flashes blue to let you know it’s cold, red when it’s too warm, and green when it’s at the desired temperature. 

The colors and size of display mean it is visible from a glance any time you pass by. It also has a full-body cage with fine lines that protect most medium and larger fish from getting burned. 

To top it off, good looking products is Fluval’s specialty.

What We Liked About This Product

  • Big temperature display
  • Full-body cage
  • Attractive design 
  • Accurate thermometer
  • 5-year warranty
  • Made by Hagen
  • Inexpensive

Why It Might Not Work for You

  • Needs a lot of flow
  • You might need two

Our verdict: 4/5 stars. Buy it.

This heater is a complicated recommendation. 

I’ve had a couple die after a short life with no warning, and it turns out that’s not uncommon. However, they do tell you when they die.

They are also more likely to stop heating than to cook your fish overnight, which is…maybe better than the other way around?

Fluval/Hagen does honor its long warranty, but you pay to send the dead one home – which isn’t cheap with a 300w aquarium heater. With the price of a new heater going down over time, it’s almost cheaper to just buy the new one.

This heater also doesn’t heat as well as it should for as many watts as it provides, even when it’s bigger than the tank needs. You need to make sure you have strong current somewhere in your tank and put the heater in it, and possibly double up, if you want it to heat properly. 

All things considered, it’s still one of the best heaters on the market, if you’re willing to deal with its problems. There are still better ones, sure, but not many.

>> Tap Here to Read More Reviews and See Today’s Price on Amazon.com <<

Hydor ETH 300 In-Line External Aquarium Heater

This in-line heater truly is the best of the bunch as far as in-line heaters go!

It heats water as it comes into the aquarium through your return line, which removes any games with determining where you get the most flow in your aquarium. Since it connects to the canister filter’s line, you won’t need to worry about how it looks in your aquarium, where it’s sitting, and at what angle.

When you do water changes, you won’t need to worry about turning off your heater ahead of time or whether your water is below any point on it since it isn’t exposed to air. 

Your fish would also have to be pretty determined to injure themselves on this heater.

While the concept of the Hydor would otherwise make it a top 3 pick, it’s just not reliable enough.

What We Liked About the Product

  • Less clutter in the aquarium
  • No searching for water flow
  • Inexpensive
  • Works with sump as well
  • Internal thermostat
  • Works with acrylic tanks

Why It Might Not Work for You

  • Short lifespan
  • Harder to double up
  • Unreliable
  • Frequently inaccurate thermostat
  • Causes leaks in filter line

Our Verdict: 3/5 stars. Buy it only if you must.

If you’re really determined to keep the heater out of your tank, especially just for weeks rather than months or years, this is likely the best in-line heater you’ll find.

However, its propensity to give out after just months by never turning off or simply turning off on its own makes it too unreliable to count on long-term.

>> Tap Here to Read More Reviews and See Today’s Price on Amazon.com <<

BEST ADJUSTABLE HEATER

#5. Aquen Pro Adjustable Heater

Aqueon Pro Series Aquarium Heater

The Aqueon Pro sports a durable plastic cover and an adjustable knob at the top, making it easy to adjust your aquarium’s temperature without moving it. With a variety of sizes, it can fit most aquariums you keep. 

Best of all, it’s got a limited lifetime warranty. Where most heaters carry a one-year warranty and are ahead of the pack with a 5-year warranty, Aqueon promises to replace your heater if it goes out, even if it’s been a decade, and they’ve been around long enough to back that promise. In many cases, you won’t even need to ship in the old one.

This is one of the best options on the market if you’re on a budget or feeling disillusioned about heaters after seeing a few too many poorly rated options.

Aqueon has a fantastic product here, but their quality control keeps them from falling into our top three.

What We Liked About the Product

  • Adjustable
  • Lifetime warranty
  • Status light (red: heating, green: not heating)
  • Low price
  • Established brand name
  • Fairly accurate
  • Reliable; often lives for 3+ years

Why It Might Not Work for You

  • Hit or miss quality
  • Habit of splitting open
  • Sometimes leaks red goo
  • Difficult to read dial

Our Verdict: 3/5 stars. Buy it on a budget.

With as many expenses as there are in fish keeping, we all want to find ways to save money and do it right without going bankrupt. Aqueon, thankfully, offers us a solution for low cost heating that isn’t a safety concern, like many budget options are.

At this price range, you’ll find the quality on these Aqueon heaters is inconsistent. You might get one that lives 1 month or one that lives 10 years. You might also have it simply fail and either cook your fish or stop heating, but it might also split open or leak a weird substance.

You’re also missing out on a lot of practical and beneficial features that more expensive heaters have.

On the other hand, it’s more often a successful purchase than not, and many people even purchase these in bulk over buying one expensive one. It’s hard to beat its reliable functionality, adjustable thermostat, and lifetime warranty at this price. This is the go-to standard option for many fish keepers for good reason.

Do keep in mind you only get one replacement on the warranty

>> Tap Here to Read More Reviews and See Today’s Price on Amazon.com <<

FORMERLY RELIABLE, NOW WITH CONCERNS

Eheim Jager

This heater was once one of the best you could buy, but manufacturing quality concerns have dropped it from our list.

Eheim Jager is a long-standing quality name in the fish keeping hobby, and has to be on any list at this point. One of the original heaters with an internal thermostat and temperature control dial, this heater can be had for a very low cost. It’s accurate and made of high-quality shatter-proof glass.

However, Eheim’s quality has been slipping lately, so this wasn’t able to make our top three. If they kept the quality up on this product, it would be a shoe-in.

What We Liked About the Product

  • Low cost
  • Classic design
  • High quality glass
  • Accurate thermostat
  • Saltwater and freshwater
  • When it works, it’s reliable

Why It Might Not Work for You 

  • Electrical concerns
  • Poor customer service
  • May fail within days

Our verdict: 2/5 stars. Do not buy.

I’d love to recommend this heater, but the Eheim’s slipping standards are a real concern. Even veteran fish keepers who once relied on this brand are concerned about the electronics and longevity of these products.

YOU GET WHAT YOU PAY FOR

Freesea

While this is small and attractive, we found that it wasn’t reliable enough and the quality isn’t very high.

FREESEA Small Aquarium Betta Submersible Heater

While this heater can heat larger aquariums, it can also be small enough to heat just 1 gallon. If you have a very small tank, this is the most popular choice.  It also has a large, easy to read LED display for the thermostat, which is controlled externally so you don’t need to remove the heater to change the temperature.

While this is a popular product and has great ideas behind it, it isn’t making it into our top three due to its lack of reliability.

What We Liked About the Product

  • Small size
  • Attractive shape
  • Visible display
  • Very low cost
  • External thermostat control

Why It Might Not Work for You

  • It might just not work
  • Covering doesn’t cover back
  • Inconsistent temperatures
  • No internal memory
  • Not a good idea for saltwater

Our verdict: 1/5 stars. Do not buy.

The design and concept of this heater is fabulous. The features are just great. In theory, it’s the perfect small heater. 

The reality is, it’s cheap and you get what you pay for. It often stops working or doesn’t stop running, and the suction cups create enough space to expose and uncovered back to a curious fish. It also doesn’t have an internal memory, so it will need to be reset every time you plug it in. 

Overall, it’s more of a hazard than a help. Whether you need a smaller or bigger heater, there are better options.

How to Choose the Best Aquarium Heater

When Bigger Is Better For Heaters

When it comes to what size to get, it’s especially hard to choose if you have a size of tank that sits at the edge of a heater’s capability. I find this most common with tank sizes like 30 gallons, 50 gallons, 75 gallons, and so on. 

If you can, err on the side of big. 

If you have a 30-gallon tank and choose a heater that does 20-35 gallons, your heater will work harder to get your water up to the right temperature.

If you have a cold house, absolutely choose the bigger heater. Your heater will have to work harder to raise a tank to 73 degrees in a 50-degree house than it will in a 70-degree house. The more you make it work, the more likely it is to encounter an issue. 

In general, you don’t want to err more than a size or so up. If your heater is designed for 100 gallons and your tank is 10 gallons, it’s oversized.

Raising The Temperature Enough Degrees For Your Fish

If your house really is 50 degrees and you’re hoping to bring it up by 20+ degrees, it’s better to get into the nitty gritty math here.

There is a formula to determine how many watts we need for an aquarium:

This equation shows how to determine how many watts you need to heat each gallon of water by how much in how much time.

It shows us that heating a 1-gallon tank in 1 hour by just 1 degree takes 3.1-watts. 

This is how we determine the rule of 3-5 watts per gallon.

However, this also depends on your house’s temperature.

Here’s an example…

If you had a 50-degree house and a 5-gallon betta tank you wanted to raise to 70 degrees, and you wanted it done in about 5 hours, you would want a 62-watt heater. 

That’s 3.1 x 5 gallons x 20 degrees divided by 5 hours.

On the other hand, most heaters are closer to 25-watts for a 5-gallon tank, which is more than plenty if you multiply 3-5 watts by 5 gallons and will do great if your house is closer to standard room temperature.

Many heaters, once you do the math, are expecting you to reach your desired temperature increase of about 3-5 degrees within 3 hours

To simplify shopping, you can divide the wattage of a heater by the gallons in your tank to determine how much it will heat your fish tank in about 3 hours.

It’s the simplified version of solving the equation above when you’re reaching your temperature in 3.1 hours, and you’ll often find it’s the inverse of 3 watts per gallon.

If there’s a larger discrepancy between your desired temperature and your house’s temperature, size up.

If you have a larger aquarium, you can do two medium heaters rather than one large one. This helps ensure that you are also protected in case one fails and protects them from wearing out due to running constantly.

What Heater Material To Choose

Glass

Heaters made of glass are less expensive, easy to find, and usually include a thermostat inside the heater. Even shatterproof glass is more fragile and can break easily. 

Glass heaters especially should also be allowed to cool before you begin a water change and acclimate before powering them on.

Titanium

Titanium is a hardy, tough material that can reach very high heats and are more difficult to damage. 

Titanium heaters usually have a separate thermostat to sense the fish tank’s temperature and adjust it. While this means you may need to buy a separate thermostat, it also means you won’t need to replace the entire heater if it fails. 

Plastic

Some heater manufacturers are starting to make their heaters completely covered in plastic. They are attractive and less likely to burn your fish.

Cords & Electronics

Any heater you choose should be safe to use. If the cord is so short that you cannot create a drip loop to prevent water from running down the cord into a power socket, it is not safe to use.

Ensure any heater you purchase is UL listed. It is, after all, going directly into water where you keep fish, plants, and even your hands.

Additional Purchases

There’s only a couple more things you may want to consider with your heater.

A Thermometer

You can get a thermometer for cheap, but you should also consider an instant read thermometer to make checking your tanks easy. Whether your thermostat is external or internal, you’ll want to catch any inconsistencies sooner than later. 

Since you can get a waterproof instant read thermometer that reads in under 3 seconds for under $20, it’s worth it. It’ll save you more than it costs.

An External Thermostat

You can get a thermostat even if your heater comes with one. Just ensure the thermometer is waterproof. If you have a saltwater tank, it should be corrosion proof as well. 

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