Updated: April 15, 2021 - By: - Categories: Equipment

Aquarium heaters are used to ensure the temperature is maintained at a steady and proper level for tropical fish. This equipment is extremely important for the fish since they are coldblooded and maintain their body temperature based on surrounding conditions. Wrong temperatures can stress the fish that leads to a significant decrease in their disease-resistant ability. In this article, you will learn what to look for when buying a new heater for your fish.

Best fish tank heaters

Model Our rating Wattage For tanks Available sizes Temperature range Features
Aqueon Aquatic Flat Heater editor's ratingAqueon Aquatic Flat Heater #ad 7.5 watts 1-3 gallons, Bettas, tropical fish 7.5/15W preset for tropical fish, can’t set
FREESEA Aquarium Heater editor's ratingFREESEA Aquarium Heater #ad 25 Watt 1 – 5 gallons, Bettas, tropical fish 25-100W 63-95°F, adjustable light indicator, include a digital thermometer
Hygger Saltwater Tank Titanium Tube Heater with Controller editor's ratingHygger Saltwater Tank Titanium Tube Heater with Controller #ad 200w 20 – 45 gallons 50-500W 32-104°F, ±0.5°C error, adjustable LED digital display controller, thermometer, Celsius or Fahrenheit reading
Fluval M Submersible Heater editor's ratingFluval M Submersible Heater #ad 100 watt up to 30 Gal 50-200W 66-86°F, adjustable light indicator, blends into the aquarium environment
Aqueon Pro Submersible editor's ratingAqueon Pro Submersible #ad 100 Watt 20-30 Gal 50/100W 68-88°F, ±1°F, adjustable LED light indicator
Orlushy Submersible Aquarium Heater editor's ratingOrlushy Submersible Aquarium Heater #ad 150W 30 – 50Gal 100-500W 68-89°F, ±1°F, adjustable LED light indicator, include a digital thermometer
Eheim Jager Aquarium Thermostat Heater editor's ratingEheim Jager Aquarium Thermostat Heater #ad 250 Watts 55-60 gallons 75-300W 64.4-93.2°F (18-34°C), adjustable operation light, recalibration, running-fry prevention
Orlushy Submersible Aquarium Heater editor's ratingOrlushy Submersible Aquarium Heater #ad 300W 50 – 80 Gal 100-500W 68-89°F, ±1°F, adjustable LED light indicator, include a digital thermometer
UPETTOOLS Submersible Aquarium Heater editor's ratingUPETTOOLS Submersible Aquarium Heater #ad 500W 60 – 120 gallons 60-90°F (15-32°C), ±2°F, adjustable external digital controller, built-in thermometer, safety shut-off
Finnex Deluxe Titanium Tube Heater editor's ratingFinnex Deluxe Titanium Tube Heater #ad 800 Watts 140 – 265 gallons 300/500/800W 0-99°F, ±2°F, adjustable external controller

How does aquarium heaters work?


Most aquarium heaters are operated using a temperature control thermostat to sense ambient temperatures and automatically open or close the electrical circuit that heats the inside heating core. In this way, the heater maintains the aquarium water at the desired temperature with very little fluctuation.

Most heaters have an LED light indicator integrated into the unit that burns whenever the heater is actually operating.

Depending on the actual room temperature and how well the system is closed down, the heater may run all the time or very little. This is the strong reason why your tank needs to have a canopy to prevent both evaporation and heat loss.

Types of aquarium heaters

Glass heater

Eheim Jager Aquarium Thermostat HeaterEheim Jager Aquarium Thermostat Heater #ad

Glass heaters are the most common and budget-friendly option in the market. They come in different lengths and wattages to suit different tank sizes. This type of heater is best known for how easy it is to set up and operate.

Ensure you choose a high-quality glass heater because it is very risky to use when the glass is made from poor-quality glass. You should ensure the heater is fully submerged in the water while operating or the glass will be broken after a short service time. Choosing a glass heater with a running-dry protection feature is strongly recommended.

Titanium heater

Hygger Titanium Tube Heater with ControllerHygger Titanium Tube Heater with Controller #ad

These are newer, higher quality additions to the market. You might have to dig deeper into your pockets for this type of heaters, but it’s worth it, considering you don’t have to worry about any breakage, shattering, and exploding.

Most titanium heaters come with a separate controller placed outside the aquarium. The controller saves you from wetting your hands every time you want to adjust the temperature.

Inline heater

Hydor In-Line External HeaterHydor In-Line External Heater #ad

In-line external heaterIn-line external heater #ad

For aquarists concerned about appearance and the unobstructed view of their aquarium, inline heaters are the best option. The most basic type features a pipe with a heating element that heats the water as it flows through. This heater is usually attached to the intake or output hose of a canister filter.

Besides staying clear from view, inline heaters are incredibly safe for you and your fish and provide even heating because the water passing through the heater circulates inside the tank and distributes the heat.

On the downside, inline heaters are more expensive, costing up to twice as much as standard glass heaters. By adding a piece into your filtration system, you increase the chances of a leak. The inline heater also needs to be placed in an upright position to prevent trapped air from compromising its performance.

Substrate heater

The substrate heater (or undergravel heater) is a heating cable placed under the aquarium substrate. The main purpose of this heater is to heat the substrate and for better water circulation.

The theory is warmer water near and among the substrate is constantly rising and replaced by cooler water near the surface, ensuring better oxygen and nutrient transport. This brings many benefits for planted tanks that are built for years of enjoyment.

However, substrate heaters are complicated to set up and maintain and rarely used these days.

Battery-powered heater

Tropical fish are sensitive to sudden temperature changes. Having a battery-powered backup heater can come in handy in case of a power loss. This heater is also used when shipping fish to keep them warm until they get to their new home.

Unluckily, because heaters require a lot of power, it is hard to find battery-powered options available on the market. As an alternative, you could use a battery backup.

How many watts per gallon for aquarium heaters?

It is important to ensure you select the correct aquarium heater for the size of your tank. The rule of thumb is for increasing up to 10°F (or 5°C) above standard room temperatures (68-72°F – 20-22°C) you will need 1 watt of heating power per liter of water (approx. 4 watts per gallon). Just double the wattage if you need to heat up to 20°F (or 10°C).

For example, a 20-gallon aquarium (75 liters) placed in standard room temperatures will need around 80 watts of heating power, and a 75-100 watt heater is a perfect option.

Following is the heater size table for different tank sizes.

Tank size To heat up to 10°F or 5°C To heat up to 20°F or 10°C
1-3 gallon 10-15 watt 25W
3-5 gallon 12-25 watt 50W
10-15 gallons 50-watt 100W
20 gallons 100-watt 150W
25-30 gallons 100-150 watt 200W
40 gallons 150-watt 300W
50-55 gallons 200-watt or two 100-watt 2 x 200W
60 gallons 250-watt or two 150-watt 500W (2 x 250W)
75 gallons 300-watt or two 150-watt 2 x 300W
100 gallons 500-watt or two 250-watt 2 x 500W
200 gallons 800-watt or two 500-watt 2 x 800W

Fish tank heater reviews

Aqueon Aquatic flat heater 7.5-watt

For nano Betta fish tanks of up to 3 gallons, the Aqueon Aquatic flat heater is an affordable choice. It’s a fully submersible heater with an ultra-thin design. It features shatterproof construction and works for both glass and acrylic tanks.

It is intended for common home aquariums with ambient temperatures around 68-72°F (20-22°C). It automatically heats the water and maintains the temperatures in a preset range for tropical fish. This can’t be adjusted, so ensuring that the room temperatures do not fall too low.

Installation of the heater is simple and straightforward using the suction cups that it comes with to position it horizontally or vertically, depending on your setup.

FREESEA aquarium heater 25-watt

This is a glass heater with an excellent range of features perfect for aquariums of up to 5 gallons. Among these impressive features is an automatic constant temperature function that keeps the water in your tank within the set temperature.

For easy and accurate temperature monitoring, the heater comes with a diving thermometer. It’s also worth mentioning the safety shutoff and overheating protection features, which are both valuable to your fish’s safety.  With a 12-month warranty, this promises to give excellent value for money.

If you have a nano fish tank, there are many options in this article: https://portlandaquarium.net/25-watt-heater/

Hygger Saltwater Tank Titanium Tube Heater with Controller

Titanium heaters are growing in popularity, especially among saltwater aquariums. Titanium aquarium heaters are known for their hardiness and resistance to corrosion, and this one is not any different. And it is also shatterproof.

Hygger Titanium Tube Heater with ControllerHygger Titanium Tube Heater with Controller #ad

The external controller with LCD displaying current and set temperatures and a thermometer are among the features that set this aquarium heater apart from the rest. It is very easy to set up, just ensure that you place the thermometer probe and titanium heating tube at different ends of the tank. This ensures accurate temperature readings.

Like most of the other options we have reviewed, this one also comes with an auto-shutoff feature. Its pinpoint accurate temperature heats the water to within -/+ 0.5°C of the set temperature.

It’s an excellent choice for both tropical and saltwater aquariums with a size of between 20 to 45 gallons. Many different options from 50 to 500 watts are also available.

Fluval M Submersible Heater 100-watt

The Fluval M Submersible heater has a unique range of features. These include a borosilicate glass with built-in reflective technology that mirrors the surrounding. It allows the heater to blend in with its environment.

It has a computer-calibrated thermostat for accurate temperature monitoring and an easy to adjust temperature control with a ceramic heat stick for fast and efficient heat distribution. Despite its slim build, the heater is rated at 100W and works for tanks of up to 30 gallons. There are also other available versions from 50-200W for choice.

Aqueon Pro Submersible 100-watt

The Aqueon Pro Submersible heater is designed for 20-30 gallon tanks. It is rated 100 watts with an accurate electronic thermostat to keep the temperature within a degree of the required parameters. The exterior of the heater is made from shatterproof, almost indestructible plastic, so you don’t have to worry about condensation or explosions.

Additional safety features include an auto-shutoff feature and indicator lights, so it is easy to tell when the heater is working. Given how short-lived most heaters in the market are, it’s outstanding that this one comes with a limited lifetime warranty.

Orlushy submersible aquarium heater 150W

The best aquarium heaters aren’t always the most expensive. There are some excellent budget-friendly options that you should consider. The Orlushy submersible aquarium heater is one of them.

This high-quality heater has a 2mm, explosion-proof quartz glass construction that ensures efficient heat distribution. It offers adjustable temperature that you can adjust in small intervals. For easy monitoring, the heater comes with a digital thermometer.

If you have a 30 to 50-gallon tank, this option will work perfectly for you. Many other sizes from 100-500W are also available for different tank sizes. They work for both fresh- or salt-water.

Eheim Jager TruTemp Submersible Heater 250-watt

The Eheim Jager spots a simple and easy-to-use design. It comes with many valuable features that make temperature management in your 55 to 60-gallon tank easy and safe.


The Eheim Jager features a TruTemp dial with small intervals on its top for easy temperature adjustment. The temperature range is broad enough to meet the needs of most types of fish people can keep in home aquariums. Unlike other heaters, it also includes a readjustment ring for you to recalibrate the heater for better accuracy after using a long period.

It is fitted with laboratory-grade shatterproof and shock resistant glass for longevity. The Eheim Jager heater has a thermo-safety feature that turns off itself when the water levels get too low. This prevents running dry and glass breakage.

Orlushy Submersible 300-watt aquarium heater

For aquarists with a sizeable tank in the range of 50 to 80 gallons looking for a quality, high wattage heater, the Orlushy submersible aquarium heater fits the bill.

The heater comes with the standard features of every decent heater. These include a temperature control knob that you can adjust in small intervals, a reliable thermostat that eases the task of keeping a constant temperature, auto shut off to prevent overheating.

The heater is made from explosion-proof, 2mm thickened quartz glass, ensuring long life and the safety of your fish. It comes with a digital thermometer for temperature control and you don’t need to buy one.

UPETTOOLS Submersible 500-watt aquarium heater

The Uppettools submersible aquarium heater has so many wonderful features you can’t skip. It comes with a submersible glass heating tube surrounded by a plastic cover and an external controller with a digital LED display.

On the right side of the controller, there is a button for you to set your desired temperature. The heater is built with an intelligent thermometer module that monitors the tank’s temperature and shows it on the digital display. So, you will see both the set and current temperatures on the digital-display controller.

Moreover, its dual CPU safety design automatically shuts off the heater when you pull it out of the water. It also has an overheat protection that turns the heater off when the water reaches the set temperature.

Finnex Deluxe Titanium Tube Heater 800-watt

Finding a heater for a 265-gallon aquarium is not easy. Finnex has one that is not only up to the task but has all the necessary features to ensure safety for you and the fish.

The Finnex Deluxe Titanium tube heater features a corrosion-resistant and explosion-proof tube that is virtually unbreakable! It is safe to use in both freshwater or saltwater aquariums.

The heater comes with an external controller for easy temperature adjustments and control. This controller can work with any heating tube with a 3-prong connector whether it’s the same brand or not.

If you have some large fish in the aquarium, you’ll be happy to know that the heater comes with a protective guard to keep the fish safe.

How to install an aquarium heater?

Step 1 – Set the temperature


Most standard aquarium heaters often simply have a knob to adjust and the unit is set. If you have tropical fish, select one in the range from 75 to 80°F (24-27 °C) based on the tank species. 78°F is ideal for most tropical tanks.

Do NOT plug it in when out of the water. Don’t just plug the heater in to see it heat up in your hand then put it right away into the water. Placing a hot tube into the water is a great way to break the glass. It is not so difficult to do. Only plug the heater in when it is fully submerged in water.

You can adjust the temperature setting once power is applied. There is no problem with this, but ensure NOT to take the heater out of the water when it is working. The sudden change between the warmed water and cooler room temperature can weaken the glass.

Step 2 – Place it in a proper position


Most aquarium heaters today are submersible and placed entirely under the water for their service life. When the aquarium is full, place the heater into position.

Do not place glass aquarium heaters in a place where it is touched by anything. The heater tube must be fully exposed to the water around it. This prevents hotspots from building up and weakening the glass where a rock or ornament prevents the even distribution of heat off the glass.

NEVER bury the heater into the gravel if it is not a substrate heater. Any wrong placements that disrupt the thermal conduction of the heater will cause the uneven distribution of heat and the tube will burst.

Aquarium heaters should be placed as directly in the filter flow as possible. This allows the heat to be pulled from the heater tube and evenly distributed around the tank as a whole. Proper current will prevent thermal layering from occurring. This is where inadequate currents are generated in the tank so some spots are left stagnant.

You can place your heater vertically or horizontally, there is no science behind this. It is convenient to place the heater horizontally, near the bottom of the tank so that it is always submerged in the water, even when you do a weekly partial water change. And you don’t need to plug it out before water changes.

Ensure that you have no problem with the tank leakages and the water level gets lower than the point where the heater element may become exposed.

Step 3 – Daily temperature verification

Zacro LCD Digital Aquarium ThermometerZacro LCD Digital Aquarium Thermometer #ad

Make sure the temperature you are trying to get is the one you get. You should always have a reliable independent thermometer to verify the temperature in the tank. Verify the reading once a day as part of your regular aquarium maintenance.

I always put my hand on the side of the tank when I verify the temperature. Over time I have come to know the temperature “by hand”. I usually know if there is something wrong before I even look at the thermometer.

Accessories and replacement components

Heater guard

This guard fits most fish tank heatersThis guard fits most fish tank heaters #ad

Also called an aquarium heater cover or mat, this is one of the essential accessories for your aquarium heater. It’s even more critical if you have a big aquarium that requires a high-powered heater.

The aquarium guard covers the heating surface of the aquarium, ensuring that fish don’t get burnt in case they touch or get trapped behind the heater. An aquarium guard can also protect you from accidentally touching the heater while conducting maintenance or a water change. The guard is often a plastic cover attached over the heating area of the heater.

Suction cups

Suction cups for aquarium heatersSuction cups for aquarium heaters #ad

Suction cups are a vital part of setting up an aquarium, and they feature prominently in aquarium heaters. The role of suction cups is solely installing and keeping the heater in place.

Using the suction cups, you can install most submersible heaters horizontally or vertically. The cups are also used in various other functions like holding filters, hoses, and decorations in place.

Magnetic suction cups

Zoo Med MagClip Magnetic Suction CupsZoo Med MagClip Magnetic Suction Cups #ad

Suction cups are affordable and easy to use. But every time you want to reposition the heater, you have to dip your hands into the aquarium not to mention, ordinary suction cups get damaged easily.

Magnetic suction cups are designed to remedy these challenges. Just like ordinary suction cups, these are easy to use, and you can reposition the heater without getting your hands wet. Magnetic suction cups also offer more longevity and better value for money.

Heater controller

Inkbird WiFi ITC-308 Digital Temperature ControllerInkbird WiFi ITC-308 Digital Temperature Controller #ad

This equipment helps reduce your work of daily temperature verification. With a heater controller, you don’t have to check your aquarium water temperature every day. The controller will regulate the water according to your set parameters automatically. Most importantly, it will prevent overheating, which can damage the heater and ‘boil’ the fish.

In case you’re concerned about the quality of your heater, using a heater controller can bring you peace of mind and make it easier to provide your fish with the right temperature. It likes a two-step temperature verification.

Frequently asked questions and common problems

How to safely remove a glass heater?

It doesn’t happen often, but sometimes aquarium heaters must be removed. If the heater has been running, it should be unplugged for at least a half-hour before being exposed to the cool atmosphere. Keep in mind that any sudden change of temperatures can deteriorate the glass and it may explode at any time without any warning.

The heater keeps falling off

This is one of the simplest but most common aquarium heater problems to fix. The suction cups are simply worn out and can’t hold the weight of the heater. The fix is as simple as buying new suction cups. Alternatively, you can opt for magnetic suction cups #ad, which last longer.

Will an aquarium heater melt plastic?

When positioned properly, heaters don’t pose any risk to plastic, especially your acrylic tank. But, if the heater is resting directly on the tank, it could burn it. It’s important to make sure the heater is not resting on the sides of the aquarium or plastic plants and decorations.

Can an aquarium heater burn fish and plants?

It is rare, but it happens. That is why you should install an aquarium guard. Also, ensure the placement of the heater is at a safe distance from plants and décor.

Can the aquarium heater touch the glass?

You should always take caution when setting up your heater to ensure it doesn’t touch the aquarium glass. Equally, the heater should not touch the gravel (unless it’s the under-gravel heater) or an ornament inside the tank. This ensures proper heat distribution and prevents damage to the décor or the heater itself.

How to hide the aquarium heater

The best way to hide the aquarium heater is to have it inside the sump. You can also hide the heater behind backgrounds, rockwork, or large décor.

Is an aquarium heater necessary for a flowerhorn?

Flowerhorns require a temperature of at least 80°F, which means it is necessary to have a fish tank heater to keep flowerhorns.

What is the best heater for saltwater aquariums?

Most fish tank heaters will work in both freshwater and saltwater. If quality and longevity are a concern, titanium heaters are the best because they are corrosion resistant.

Energy consumption and running cost

The energy and consumption of a heater depend on its watt rating. The more the watts, the higher the energy consumption and running costs.

For example, a 100-watt heater will consume about (100W x 24 hours x 365 days)/1000 = 876 kWh annually. With the average electricity rate of 13.6 cents per kilowatt-hour, it costs approximately $119 annually, approx. $10 monthly.

The real number is smaller, based on how many hours the heater works in a day. This is based on the ambient room temperature and how effective your aquarium keeps heat. Having a lid helps the tank keep heat better and save a lot of cost running the heater.

How to repair an aquarium heater?

Aquarium heaters are water-tight, taking apart a heater can compromise its seals allowing water to sip into the heater, causing it to short-circuit. In most cases, it’s best to replace the heater if it fails. While it’s possible to repair the heater, it’s not worth the risk it poses to you and your fish.

Overheating aquarium heater

Several factors could lead to overheating. It is possible the heater is too powerful for your tank. In this case, you need to get an alternative heater with a lower power rating.

If that’s not the case, you should also check to ensure the adjustable heat setting is within the right temperature and check the thermometer to ensure it’s working correctly. If none of these is causing the problem, it’s possible your heater is malfunctioning and needs to be replaced.

The indicator light is on but the heater is not working

The reason is usually a loose or disconnected contact. Unfortunately, there’s not much you can do about that. If the heater is still under warranty, you can send it back to the manufacturer to get a replacement.

Hissing or a clicking noise

Heaters shouldn’t make a sound. However, some designs make a clicking noise when the thermostat kicks in. When the clicking sound is continuous or happens at any other time, your heater could be failing.

The hissing sound points to a more serious problem. Hissing can be caused by failed seals that let water sip into the heating chamber. When the cold water touches the hot element, it produces a hissing sound as it evaporates.

In cases where the leaking is significant, you can hear a knocking or popping sound, which is water inside the heater boiling. In all these cases, you should have the heater replaced immediately.

How often should you replace your aquarium heater?

The expiration of your heater depends on its quality. Some can last for many years, while others have shorter longevity. A general rule of thumb is to change the heater every two years just to be on the safe side.

Lucas has been keeping successful fish, planted, and reef tanks for many years. He loves to collect aquatic organisms and keep as many aquariums as he can.

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