Many aquarists use 40 gallon aquariums as normal display tanks, but also as breeders for raising fry and juvenile fish. So it’s particularly important to maintain a steady temperature by using the best aquarium heater for 40 gallon tank setups.
The team and I have owned various tanks of this size over the years, along with many different heaters! We carefully assessed some of our top choices for 40 gallon tanks and chose the Fluval M150 Submersible Heater as the winner overall.
Read on to find out why, along with our reviews of a range of other excellent options. Whether you prefer a digital, analog, or even an external heater we’ve got you covered!
- Best Even Heating: Fluval M150 Submersible Heater
- Best Digital Alerting: Fluval E200 Electronic Heater
- Best External Heater: Hydor 200W Inline External Heater
- Best For Breeder Tank: Orlushy 200W Submersible Aquarium Heater
- Best Shatterproof Analog: Aqueon Pro 150W Adjustable Heater
- Best For Manual Calibration: Eheim Jager 125W Aquarium Heater
Best Aquarium Heater For 40 Gallon Tank Setups Reviewed
All the heaters below have been assessed against key criteria for their suitability in your 40 gallon aquarium. So as well as power, this includes accuracy, temperature stability, and safety features such as overheating and run-dry sensors.
1. Fluval M150 Submersible Heater
- Heater Type: Submersible, adjustable
- Dimensions: 13.0 (length) x 1.0 (diameter) inches
- Wattage: 150 Watt (other wattages available)
- Key Features: Temperature range of 66 to 86°F, easy-control temperature dial, computer-calibrated thermostat, ceramic heat sink, heating indicator light, shock-resistant glass
- Best For: Even Heating
Fluval M Series heaters are a modern take on the traditional glass submersible heater. At 150 Watts, the M150 gives plenty of power for your 40 gallon aquarium. And the ceramic heat sink around the heating element gives even and consistent heating at an affordable price.
It’s suitable for freshwater and saltwater aquariums and is made of borosilicate shockproof glass. So it will withstand any knocks during maintenance or from aggressive fish like some cichlids.
Note, it doesn’t have an overheat or auto cut-off function if it’s allowed to run dry. So, like any glass heater, do ensure it stays fully submerged to avoid breakage. But it does have an indicator light showing when it’s actively heating, making it easy to identify potential faults.
The slim 1.0-inch diameter and 13.0-inch length give it a sleek look and make it easy to fit into even a shallower 40 gallon breeder tank while still giving you plenty of room for fry. It will also fit well into most hidden filter compartments if your tank has one.
It has a clear adjustment dial on top of the heater which is easy to access. And the 3-degree increment markings make setting an accurate temperature simple too. Overall many owners praise M heaters for their power and even heating at the price.
2. Fluval E200 Electronic Heater
- Heater Type: Submersible, adjustable, digital/ electronic
- Dimensions: 14.0 (l) x 2.0 (w) x 1.12 (d) inches
- Wattage: 200 Watt (other wattages available)
- Key Features: Temperature range of 68 to 93°F, adjustable in 1°F increments, two digital temperature sensors, LCD screen with VueTech color alert system, bumper guard
- Best For: Digital Alerting
The Fluval E200 is an adjustable, digital 200 Watt heater with a temperature range of 68 to 93°F. So whether you use your 40 gallon aquarium as a display or breeder tank you can set a precise temperature for your fish or fry, adjusting it in 1°F increments.
It has a clear LCD screen and features Fluval’s VueTech color alert system. The display shows green if the temperature is correct, but will change to red if it’s over 2 degrees too high, and blue if too low. So you can easily avoid any temperature issues that may harm your fish.
At 14.0 (l) x 2.0 (w) x 1.12 (d) inches it will easily fit a 17 inch high 40 gallon aquarium, or a shallower breeder tank at a slight angle. And the integrated bumper guard keeps your fish well away from the heating element. So peace of mind that your fish won’t be harmed.
The strong suction cups and adjustable bracket make installation easy. And whilst it’s designed to go onto the back wall of your tank, there’s also a side mounting bracket. So you can choose where to position it based on your tank’s layout.
Some owners report that placement can be tricky with this heater as you need to mount it at the right position from your filter to circulate the water. But many praise the E200 for maintaining a stable temperature while being easy to set up and calibrate.
3. Hydor 200W Inline External Heater
- Heater Type: External inline, adjustable
- Dimensions: 12.5 (l) x 4.0 (d) x 4.0 (w) inches
- Hose Sizes: ½ inch, ⅝ inch
- Wattage: 200 Watt (300 Watt also available)
- Key Features: Temperature range of 65 to 93°F, electronic temperature dial, built-in thermostat, hanging eyelet, LED heating indicator
- Best For: External Heater
The Hydor Inline External Heater is fitted on the outflow from your sump filter or canister filter and is fantastic if you want less equipment in your tank. It’s freshwater and saltwater compatible so is perfect if you want more space in your 40 gallon tank for fish or corals.
The 200 Watt version is plenty powerful enough for a 40 gallon aquarium, and because it constantly heats the outflow water from your external filter, it provides a consistent temperature throughout your tank. So it’s great for sensitive marine fish and invertebrates.
Hydor uses a PTC (Positive Thermal Coefficient) polymer to construct the heating element. This material becomes non-conductive above its maximum temperature of 93°F. So there’s no risk of overheating your fish.
It’s supplied with ½-inch and ⅝-inch connectors, so will fit most canister hoses. And while some users have reported leaks during initial setup, it’s usually due to a poor seal. To get the best seal, soak your hoses in hot water to expand them before clamping the connectors tightly.
The Hydor has a temperature dial with adjustments in 2-degree increments. So it’s easy to set an accurate temperature from 65 to 93°F, all without having to reach inside your tank!
And many users praise the Hydor for its accuracy and even heating throughout their aquarium.
4. Orlushy 200W Submersible Aquarium Heater
- Heater Type: Submersible, adjustable
- Dimensions: 11.0 inches (length)
- Wattage: 200 Watt (other wattages available)
- Key Features: Temperature range of 68 to 89°F, built-in thermostat, separate digital thermometer, 2mm thickened shatterproof quartz glass, 6 ft power cord
- Best For: Breeder Tank
The 200 Watt Orlushy Submersible Aquarium Heater provides ample power for your 40 gallon tank, and as the least expensive in our list is great if you’re on a budget. Despite the price, the 2mm thickened shatterproof quartz glass makes it very durable against any knocks.
At just 11.0 inches in length, it’s also the shortest submersible heater here. This makes it a great choice if you own a shallow 40 gallon breeder tank as it will fit with ease. And while some owners report the suction cups can break, they can be easily replaced.
The Orlushy has an indicator light showing when it’s actively heating your water. And it’s easy-to-access control knob located at the top is marked in clear 2-degree increments. So you can easily read and set your required temperature.
With a range of 68 to 89°F, we found the Orlushy capable of maintaining a consistent temperature of around 75°F. It can be less accurate if you run it constantly at its top setting though, so we recommend keeping it in the mid-range.
Some owners also report that this heater can be inaccurate by up to around 4°F. So do keep a separate thermometer in your tank to check. Overall though, many remark that the Orlushy keeps a consistent temperature once set for an affordable price.
5. Aqueon Pro 150W Adjustable Heater
- Heater Type: Submersible, adjustable
- Dimensions: 12.75 (length) x 1.5 (diameter) inches
- Wattage: 150 Watt (other wattages available)
- Key Features: Temperature range of 68 to 88°F, electronic thermostat, LED heating indicator, run-dry and overheat shut-off, thermal plastic shatterproof casing, limited lifetime warranty
- Best For: Shatterproof Analog
The Aqueon Pro 150 Watt heater can be mounted vertically or horizontally, and at 12.75 inches it’s great for 40 gallon display or breeder tanks. While the top of the heater is 1.5 inches, the heating tube itself is even slimmer so it won’t obstruct your fish or plants.
Unlike many analog heaters of this type, the heating tube is made from shatterproof thermal plastic rather than glass, making it highly durable. So there’s no danger of cracks or breakages if you accidentally knock it.
It has a red indicator light clearly placed at the top to show when it’s actively heating. And as well as automatically shutting off if it runs out of water, it will shut down if it overheats. So peace of mind that you won’t accidentally run it out of the tank or overheat your fish.
The adjustment dial is well located at the top and easy to turn. But because the numbers, marked out in 4-degree increments, are the same black color as the dial it does make it a little hard to read.
But the Aqueon Pro holds a stable temperature thanks to the electronic thermostat which is accurate to +/- 1°F. And though some owners have reported issues after 6 months, these have been resolved with the lifetime warranty and excellent support.
6. Eheim Jager 125W Aquarium Heater
- Heater Type: Submersible, adjustable
- Dimensions: 12.2 (length) x 1.4 (diameter) inches
- Wattage: 125 Watt (other wattages available)
- Key Features: Temperature range of 65 to 93°F, built-in thermostat, calibration dial for temperature adjustment, heating indicator light, run-dry shut-off, shatterproof glass
- Best For: Manual Calibration
If you want the ability to manually calibrate your heater for your 40 gallon aquarium, the Eheim 125 Watt is an excellent choice. Although manual calibration can take a little getting used to, we found it to be one of the most accurate analog heaters. Great if you have sensitive fish!
So as well as the large easy-to-read temperature dial, split into 1°F increments, you can turn the separate calibration indicator to your actual current temperature. This improves the accuracy of the Jager and ensures a consistent temperature for your fish.
Note that although the Jager is slim at 1.4 inches, it’s longer than most for the wattage. At 12.2 inches, this 125 Watt version is fine for most 40 gallon tanks. But if you choose a higher wattage be careful to check your measurements.
It has a clear indicator light so you can see when it’s actively heating and identify any faults. A run-dry sensor is also included. So if you accidentally leave it above the water level when switched on it will cut out rather than shatter.
There is no overheat sensor though, so we recommend using a separate thermometer in your tank and checking it daily. But overall many owners praise the Jager for its accurate and steady temperature at a reasonable price.
Buyer’s Guide To The Best Aquarium Heater For 40 Gallon Tank Setups
Before making your decision on the best aquarium heater for your 40 gallon tank, there are a number of factors you should consider.
Benefits Of The Best 40 Gallon Aquarium Heater
There are several benefits to choosing the best aquarium heater for a 40 gallon tank. This applies whether you keep a display tank or a breeder tank where you may need a higher temperature for your fry:
- Even And Stable Temperature: Maintaining a consistent temperature, usually around 74 to 80°F, and heating your tank evenly is critical for tropical fish. Even with goldfish that can tolerate around 64°F, using a heater will keep it stable.
- Full Temperature Control: Choosing the best aquarium heater for 40 gallon tank setups lets you change the temperature based on your fish. So you can switch your display tank to a breeder later on and increase the temperature for the fry.
- Prevent Temperature Fluctuations: Unlike in larger bodies of water in nature, your 40 gallon aquarium is subject to temperature fluctuations. The best heater for 40 gallon tanks will prevent this, not only in winter but if your room cools overnight too.
- Reduce Stress And Disease: Temperature fluctuations of just +/- 2°F can put stress on your fish and aquarium plants, leading to disease. The right heater will stop this from happening.
Wattage Needed For Your 40 Gallon Aquarium Heater
Most aquarists use the general rule that the power, or Wattage (W), needed for their aquarium is between 2.5 and 5 Watts per gallon . This would mean you’d need between a 100 and 200 Watt heater for your 40 gallon tank.
But it’s difficult to choose the best aquarium heater for 40 gallon tanks based on this alone, as room temperature also makes a difference. Say your room is 65°F and you need your tank at 80°F, a 150 or 200 Watt heater is likely to be needed.
If in doubt always check the manufacturer’s recommendations to be sure.
Size And Placement Of Your Heater
Standard rectangular 40 gallon tanks can be about 37.0 x 17.0 x 17.0 inches, but breeder tanks can be shallower. Given the maximum length of a heater for tanks this size is about 14.0 inches you shouldn’t have a problem, but do check your measurements.
It’s important to position your heater correctly too. Many submersible heaters for example perform better horizontally. Or if placed vertically most should be at a slight angle. Follow the heater’s instructions to ensure you get the placement right.
Should You Use More Than One Heater?
There are some benefits of using two heaters in your 40 gallon fish tank instead of one. By positioning them at either end of your tank it can help heat your water more evenly. Plus one can act as a backup if the other fails.
But while some aquarists recommend this, it’s not essential in a 40 gallon aquarium. As long as you have the correct wattage and check your temperature daily, a single heater is fine in most cases.
If you do choose to use two, make sure the total wattage is in line with what’s required for a 40 gallon tank. For example, use two 75 Watt heaters to add up to a total of 150 Watts.
The Best Type Of Heater For 40 Gallon Tanks
The following types are the best aquarium heaters for 40 gallon tank setups. Let’s look at them below.
Submersible Aquarium Heaters
As with other tank sizes, one of the best aquarium heaters for 40 gallon tank setups are submersibles. They have a coiled heating element that sits inside a glass or metal tube. And as they are fully submerged in your water they are excellent at keeping a precise temperature.
There are many submersible digital aquarium heaters suitable for 40 gallon aquariums, with wattages of 100, 150, and 200 Watts. These are highly adjustable, some within 0.5⁰F. So you can keep a very precise temperature, for example, if you are breeding fry.
Inline And In-Sump Heaters
A 40 gallon tank is the minimum size we’d recommend for an inline heater as they generally have a wattage of 200 Watts and above. Inline heaters sit outside your aquarium, installed on the outflow from your external filter. They are great for even heating while decluttering your tank.
If you own a 40 gallon saltwater aquarium you may choose to use a sump underneath. This smaller tank houses your filtration equipment and can also contain an in-sump heater. In this way, you can leave more display room in your main tank.
Heaters Unsuitable For 40 Gallon Tanks
You may also find the following type of aquarium heaters during your research, although they are much less common. We do not recommend them for 40 gallon aquariums.
Immersible Or Hanging Heaters
Hanging or immersible heaters are very uncommon for 40 gallon or larger aquariums, although you may see them as part of smaller starter fish tank kits.
These heaters hang off the back rim with the controls out of the water and the heating element submerged. Unlike submersibles, they are quite inefficient at maintaining a consistent temperature, particularly in a 40 gallon fish tank.
Again substrate heaters are much less common today, although they can be a useful secondary heater if you own a planted tank.
Substrate heaters consist of a heating wire fixed underneath your substrate and are only designed to provide heat to your plant’s roots. By heating the substrate they help circulate nutrients and promote plant growth.
They aren’t powerful enough to heat your main tank though, particularly in a size like a 40 gallon aquarium.
Choosing The Best Aquarium Heater For 40 Gallon Tank Setups
Now let’s look at some of the key features to look out for when choosing the best aquarium heater for 40 gallon tank setups.
Temperature Stability And Consistency
Keeping a consistent temperature is key for tropical fish, but it can be even more important if you use your 40 gallon tank as a breeder. Many fry and juvenile fish are particularly sensitive to temperature fluctuations of even +/- 1⁰F.
Submersible heaters can be some of the best aquarium heaters for 40 gallon tanks. Their fully submerged and direct contact with the water helps to keep a very stable temperature. Inline heaters are also very efficient at delivering a consistent temperature to your tank.
Adjustability And Readability
While there are certainly 150 to 200 Watt preset heaters available, they are not necessarily the best aquarium heater for 40 gallon tank setups. Preset heaters can be a great option in smaller tanks, particularly if you don’t want to worry about calibration.
But in a 40 gallon aquarium it’s much better to have precise control and the ability to adjust your temperature. So look for adjustable analog heaters with an easy-to-use control knob at the top, or a digital heater that will allow you to make adjustments, often of 1 or even 0.5⁰F.
Make sure your chosen heater also has either a display if it’s digital, or if analog, a clear numerical dial so it’s easy to adjust and read the temperature accurately.
Ease Of Installation And Calibration
Many submersible heaters, whether analog or digital, are quite easy to physically install in your 40 gallon aquarium. It can be useful to check the quality of the suction cups on the mounting though, as these can sometimes tear.
Inline aquarium heaters can be harder to set up though. Make sure you install them vertically to prevent bubbles and potential cracks. And, as these are external heaters, ensure the inflow and outflow hoses are tightly sealed to prevent leaks.
Digital heaters are often easy to calibrate. Simply place them in your tank and their built-in thermometer will control the heater to bring your water to the desired temperature. Most analog heaters are similar, but check the manufacturer’s guidance as some require manual calibration.
Many of today’s digital aquarium heaters have LED or LCD displays to show when your heater is actively heating vs. on standby. While a screen isn’t essential, if you choose an analog heater, make sure there’s an indicator light to see when it’s actively heating.
Some of the best aquarium heaters for 40 gallon tanks also have overheat and run-dry cut-offs if they get too hot or run above the water level. This is particularly useful in submersible heaters as they are at risk of cracking or exploding if they run out of water.
A bumper guard is also useful to stop your fish from coming into contact with the heater and causing themselves harm. Don’t worry if your chosen heater doesn’t have one though as you can often purchase separate guards.
Materials, Durability, And Price
External in-line aquarium heaters are usually made from tough, heat-proof plastics that are highly durable. Similarly, digital heaters often use titanium housings around the heating element giving them a long life.
Many analog heaters use a more traditional glass heating tube, so if you go for his type look to see that they are shockproof. Quartz or borosilicate glass is often used in the best aquarium heaters for 40 gallon tanks as it is toughened and resistant to shattering.
Analog submersible heaters for 40 gallon aquariums tend to be less expensive than digital heaters. For example, you may pay around $35 for an analog submersible of 150 to 200 Watts, but a digital or in-line heater could be double that price.
Whether you own a display or breeder, the best aquarium heater for 40 gallon tank setups needs to provide the right power for consistent and accurate heating.
Our top choice for a 40 gallon aquarium is the Fluval M150 for its ability to evenly heat your tank without the need for manual calibration at an affordable price. Or if you want to save space for your fish, the Hydor 200W Inline External Heater is a fantastic option.
Whichever you choose, remember to check the physical measurements of your tank and use our guide to the correct wattage, taking into account your room temperature.
Find the answers to the top frequently asked questions when choosing the best aquarium heater for 40 gallon tank setups here!
What’s The Best Heater For 40 Gallon Tank Setups?
A submersible heater of 150 to 200 Watts like the Fluval M150 is the best aquarium heater for 40 gallon tank setups. But do check the manufacturer’s recommended wattage for the tank size.
Should I Use Two Heaters In My 40 Gallon Aquarium?
It’s not essential to use two heaters in a 40 gallon tank, although it allows one to act as a backup if the other fails. If you do use two, ensure the total wattage across both is within 200 Watts.
What Temperature Should My 40 Gallon Tank Be?
Most tropical fish need between 74 and 80°F depending on the species. If you have a breeder tank it’s likely to be towards the higher end. Guppy fry for example need an average of 77⁰F.
How Do I Check My Heater Is Working Properly?
The best aquarium heaters have an indicator light or digital display showing when they are active. Check your tank’s temperature daily along with this indicator to ensure it’s working.