Best Aquarium Heaters & Thermometers – Reviews & Guide

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Most freshwater fish come from tropical environments and require an aquarium heater to maintain the water temperature in the mid- to high-seventies or low-eighties degree Fahrenheit. With or without tropical fish in your tank, a heater with a quality thermometer will also help to control and prevent the temperature fluctuations in your fish tank that cause stress and harm to your fish. In this review, I will provide you some of the best fish tank heaters from different types and sizes as well as the guide to choose the right heater and use it in a proper way.

Types Of Aquarium Heaters


Submersible aquarium heater

A submersible heater is one that works within aquarium water and can be placed anywhere in the tank with suction cups. It is the most popular and affordable type of aquarium heaters on the market today. Submersible heaters usually feature an adjustment knob on their top for setting your desired temperature. After setting your submersible heater to an optimal temperature for your fish, just position it in a suitable place in your aquarium and plug it in.

easy to use - Editor's Choice
  • easy to install and use
  • accurate heater that removes clutter from your tank
  • has enough power
  • reliable
  • great quality

An in-line aquarium heater is one that is inserted into the return hose of a filtration system (canister filterwet/dry filtration system…). Whereby, the water is heated to a desired temperature before it is returned to the aquarium. It is a great option for medium to large tanks with a canister filter or a sump filtration system.

Durable - Editor's Choice
  • it holds temp where it needs to be
  • The temperature control is precise
  • accurate and less obtrusive looking in the tank
  • very easy to use
  • Durable heater

Another type is a controller heater which comes with a hang-on controller and a heating tube. The controller works outside the aquarium and controls the work of the heating tube. The heating tube is submerged in aquarium water to heat it to a temperature controlled by the controller. This type of aquarium heaters is usually designed with high wattages for large aquariums. They are ideal to keep an optimal temperature for large to extra-large fish tanks.

How To Choose The Right Aquarium Heater Size?

You will need a heater that delivers 3 to 5 watts per gallon of aquarium water. Ambient temperature is an important factor in selecting an aquarium heater. Following is a table which helps you to find the right heater wattage fit for your aquarium size.

Tank Size

To heat 9ºF/5ºC

To heat 18ºF/10ºC

To heat 27ºF/15ºC

5 gal/25 L

75 gal/300 L

50 watt

75 watt

10 gal/50 L

50 watt

75 watt

75 watt

20 gal/75 L

50 watt

75 watt

150 watt

40 gal/150 L

100 watt

150 watt

300 watt

50 gal/200 L

150 watt

200 watt

two 200 watt

65 gal/250 L

200 watt

250 watt

two 250 watt

75 gal/300 L

250 watt

300 watt

two 300 watt

Example: My 20-gallon aquarium is in a room with ambient temperatures of about 68 degrees Fahrenheit and I want to heat it to 77 degrees Fahrenheit. That means I need to heat it 9 degrees Fahrenheit. Based on the previous table, a 50-watt heater is just enough for my tank.

ideal for nano tanks up to 5.5 gallons
  • Type: submersible heater
  • Wattage: 25W
  • Temperature range: 68 °F to 82 °F
  • Ideal for: nano tanks up to 5.5 gallons, Betta tanks.
Ideal for both saltwater and freshwater
  • Type: fully submersible
  • Temperature range: 68 to 88°F, accurate to ±1°F
  • Special features: indicator light, auto shut-off
  • Used for: both saltwater or freshwater
  • Available sizes: 50W (10 gal) , 100W (20-30 gal), 150W (45 gal), 200W (50-55 gal), 250W (60-65 gal).
Ideal For Both Fresh Or Saltwater
Has Heater Controller With Heating Tube
  • Type: heater controller with heating tube
  • Temperature range: 0-99°F, ±2°F
  • Other features: audio alert system, Celsius & Fahrenheit reading, indicator lights, heater guard
  • Available sizes: 300W (40 – 80 gal), 500W (70 – 130 gal), 800W (140 – 265 gal).
Ideal For Both Marine And Tropical Aquariums
  • Type: in-line external heater
  • Temperature range: 18-34°C
  • Hosing: many options for choice
  • Available sizes: 200W, 300W
  • Used for: both marine and tropical aquariums.
Cheap And Affordable Option For Tropical Fish
  • Type: submersible
  • Temperature: preset to 78 degrees Fahrenheit, can’t be adjusted
  • Other feature: indicator light
  • Recommend: cheap and affordable option for tropical fish
  • Available size: 50W (2 – 10 gal), 100W (10 – 30 gal), 200W (40 – 55 gal).
Ideal For Both Salthwater Or Freshwater
  • Type: submersible
  • Special features: protect against running dry, on/off indicator light, made of shock resistant and shatterproof glass.
  • Used for: both saltwater or freshwater
  • Available sizes: 50W (for 7-16 gal tanks), 75W (16-26 gal), 125W (40-53 gal), 150W (53-79 gal), 200W (79-106 gal), 250W (106-159 gal), 300W (159-264 gal).
Ideal For Both Freshwater Or Marine Tanks
  • Type: submersible
  • Temperature range: 68 to 93°F
  • Special features: Fahrenheit and Celsius reading, colored display alert system
  • Used for: both freshwater or marine tanks
  • Warranty: 5-year warranty
  • Available sizes: 100W (up to 30 gallons), 200W (65 gal), 300W (100 gal).
Has Borosilicate Glass Enclosure With Reflective Technology Features
  • Type: fully submersible
  • Temperature range: 19-30°C
  • Special features: borosilicate glass enclosure with reflective technology
  • Warranty: 3 year warranty
  • Available sizes: 50W (up to 15 gallons), 100W (30 gal), 150W (45 gal), 200W (65 gal).

Best Aquarium Heater Reviews


  • adjustable temperature
  • great heater for smaller tanks
  • works very exceptionally well and very consistent
  • great quality

Betta fish tanks usually come with the small profiles, 2.5 – 3 gallons. Some nano Betta bowls are even smaller than 1 gallon that makes choosing a heater for the tanks a difficult work. Luckily, this heater works well for nano tanks up to 5.5 gallons.

With this heater, you can pick a temperature from a range of 68 to 82 degrees Fahrenheit, which is broad enough to respond the requirements of various tropical fish types. There is a temperature adjustment knob on the top for you to easily set your desired temperature. Its on/off pilot light indicator will illuminate to help you know when the heater is working.

Pro Tip

This submersible heater is built with impact-resistant glass and water-proof sealing for added safety and durability. It is very safe to use this small heater with small fish because its bumper guard protects the fish from getting damages due to contacting the heating core. It is also very easy to install with the use of a suction cup bracket provided.

If you own a nano fish tank or Betta tank, find another option for your tank here:


  • reliable tank heater
  • sturdy and well built product that performs well
  • works great even under strong conditions
  • maintains the temperature well
  • very solid heater

Designed for elegance, safety and the most performance, Aqueon Pro heater is one of the best equipment for creating a perfect condition for your aquarium fish and plants. It is designed with an electronic thermostat and is precisely calibrated for accurate temperature settings. It offers a temperature range from 68 to 88°F with the accuracy to +/- 1°. It is very easy for you to use the heater, only turn its top adjustment knob to set your wanted temperatures.


A big feature for this aquarium heater is its high-quality construction which makes it nearly indestructible and shatterproof. It is designed with an auto shut-off feature to protect itself against abnormal uses. When the water level in your aquarium decreases to under the minimum water level of the heater, it turns itself off to prevent damage by running dry. Its monitor light turns red when heating and green when not heating (the set temperature is reached or abnormal uses).


indicator light

Pro Tip

The package comes with suction cups for you to safely install the device. It can be placed vertically or horizontally into the tank and is fully submersible. There are many sizes from 50 to 250 watts for aquariums from small to large. While the 50 watt heater is ideal for a 10 gallon fish tank, the 250 watt can be used for aquariums up to 75 gallons.

Cobalt Aquatics Neo-Therm heater - safe and reliable


  • easy to use
  • easy to set an exact temperature 
  • easy and accurate heating

If you are finding a heater that can provide the most precise temperature range for your fish tank, this heater is the best option with its accuracy to ±0.5°F. The Cobalt Aquatics Neo-Therm heater comes with a modern and super flat design that gives it a very unique and attractive look.


It has a button on its top for you to set the temperature you want in your fish tank. Its LED display is able to show not only the temperature you set but also the actual water temperature in your aquarium. It offers a very broad temperature range from 66 °F up to 96 °F that you can choose the best one for all types of fish in your aquarium.

Pro Tip

For reliability and safety, the Cobalt Aquatics Neo-Therm is built with an integrated thermal protection circuitry which automatically shuts it down to prevent overheating. The heater is also durable and indestructible with its shatterproof outer casing. It can only be placed vertically in your tank and it is fully submersible. The package includes suction cups for you to easily install the heater.


  • easy to install
  • easy to use
  • safe

Featuring an advanced technology, the Finnex Digital heater is sold as a combination of an HC-810 temperature digital controller and a titanium heating tube. The controller is placed outside your aquarium, it controls the work of the titanium heating tube which is fully submerged in water. The controller offers a precise temperature control with user-friendly digital display. The titanium heating tube is incorporated in a protective guard to ensure the safety of your aquarium friends and the surrounding environment.

Pro Tip

This highly innovative heater is equipped with three-prong power receptacles that can work with Finnex titanium tubes as well as other heating elements from other brands. Another beautiful feature is the memory, which resumes the preset settings. They also have an audio pitched alert system which sounds when the temperature rises above or below the desired range. Suction cups are also included for the fast and easy installation.


  • ideal for both marine and tropical aquariums
  • easy installation
  • accurate heater that removes clutter from your tank
  • in-line external heater

Unlike other aquarium heaters in this list, the Hydor in-line external heater is meant for external use only. It is recommended to install this heater in the return hose of your filter, it could be a canister filter or a Wet/Dry sump filtration system. This in-line heater will heat the water that goes through its internal hose. By this way, the water is heated to a desired temperature before it is returned to the aquarium. This also ensures that the heated water is distributed thoroughly to your entire aquarium.

Pro Tip

This heater can be used for both marine and tropical aquariums. It is easy to use as it has a friendly user interface. The product features a high precision electronic temperature control which allows you to pick a precise temperature for your fish. You do not have to worry about overheating because its self-limiting PTC heating element ensures maximum safety against any risk of this problem.

Tetra HT Submersible Aquarium Heater - cheap and affordable


  • Great heater for a small tank
  • very reliable
  • fully submersible
  • very easy to use

The Tetra HT submersible aquarium heater is fairly cheap; however, it is capable of maintaining the water temperature at a stable range around 78 degrees Fahrenheit to protect your fish tank from temperature fluctuations. It is preset to maintain the water at a specific fixed temperature of 78 degrees Fahrenheit, which is suitable for most types of freshwater tropical fish.

The Tetra HT aquarium heater features an indicator light that is meant to let you know whether the unit is working properly or not. When the light is red, it shows that the unit is in the process of heating the water. When it is green, it means the proper temperature has been reached.

Pro Tip

By simplifying the option for adjusting temperatures, this heater is a great choice for those who are finding a cheap and easy to use aquarium heater for their tropical aquariums. It is very easy for you to install the heater with a suction cup included in the package. You can install it both vertically or horizontally as you want.


  • used for both freshwater and saltwater
  • quality german heater
  • very stable temperature

The EHEIM Jager aquarium heater is manufactured with a new TruTemp technology for more precise temperature adjustments. Its jacket is made from special glass which expands the heating surface, acts as a heat shield and also ensures that the heat emitted is distributed evenly. The design makes it effective in keeping a stable temperature in a large fish tank for the healthy growth of livestock.

The heater is made of rigid special laboratory glass, which is shockproof and shutter-resistant. It is fully waterproof, fully submersible and certified by UL, an American safety consulting and certification company. It features a Thermo Safety control, which automatically shuts it off when out of the water to protect itself from running dry damages. The on/off lamp on its body indicates the working status of the heater, thus allowing to better control it.

Pro Tip

It comes with a long cable, a clamp, and two suction cups for easy installation. There are many sizes for different tank sizes up to 264 gallons.

Fluval E Electronic Heater - perfect heater


  • ideal for both freshwater and marine tanks
  • accurate heater with LED temp display
  • easy to use heater

This is an interesting heater with many unique features manufactured by Fluval. It features dual temperature sensors that provide the precise and real-time reading of water temperatures. Moreover, it owns most advanced features of a modern heater such as LCD temperature display, fast heat technology built with a safety shut-off feature, integrated fish guard, colored display alert system, slim profile mounting bracket.

The LCD display system is a unique feature of this model. It displays real-time water temperatures during normal operation. The LCD display is also able to change its color to alert you when the temperature varies over 2 degrees F from the pre-set one. This alert function helps to remove any potential risks of temperature fluctuations for your aquarium friends.

Pro Tip

The heater has an integrated fish guard system which prevents your aquarium inhabitants to come near the heater core. The guard also protects the heater from getting damaged by large fish species. It is built with a secure mounting bracket with suction cups for easy and secure setup.

Fluval M Submersible Heater - reliable and stable


  • reliable and stable heater
  • amazing and easy to use
  • good value and a high quality heater
  • accurate and hassle free

The Fluval M aquarium heater is designed for aesthetics and durability with its borosilicate glass enclosure. The durable glass enclosure not only resists shock damages but also reflects the surrounding colors, thus making the heater blend into the aquarium environment and not compromising your beautiful aquascape.

Pro Tip

The heater is also designed for efficiency and easy installation. Its heating core is fitted with a high-density ceramic heat sink for better heating efficiency and distribution. Its thermostat is well calibrated for more precise temperature settings. It features an adjustment dial on its top that allows you to regulate the thermostat and set the heater to an appropriate temperature for your fish.

Three Types Of Aquarium Thermometers

Besides using a good fish tank heater, an accurate thermometer is also necessary for you to control the work of the heater or verify the temperature setting on a daily basis. They exist in a variety of types:

works fantastic - Editor's Choice
Great Thermometer - high quality
  • very accurate
  • safe for samll betta tank
  • easy to read
Accurate - Best Value
  • accurate readings and simple
  • descent stick on thermometer for fish tanks 
  • easy to use

The Digital aquarium thermometer is the most accurate and popular type. It comes with a probe connected to an easy to read LCD screen. It is powered by one LR44 button cell and very easy to use. Only submerging the probe into the water and the LCD screen will show the temperature of your tank water.

The Marina floating thermometer is another type of thermometers. When you put it into the aquarium water, the level of the red solution inside the thermometer indicates the water temperature. It comes with a suction cup attached to a glass tube. The glass tube will float upright with just the top of it out of the water. If you want to fix it in a place, using the suction cup to stick it to the inside wall of your aquarium.

The final type is the stick-on thermometer, which can be attached to the outside of the tank, is also popular. These thermometers are usually all black; however, they will change the color according to temperature. Just peel and stick it outside of your aquarium and a blue spirit will appear for you to read the temperature.

Do Your Fish Tank Need A Heater?

Fish are cold blooded like reptiles and they maintain the same body temperature as their environment. It is extremely important to maintain constant temperatures. The temperature will affect metabolic rates of fish and their desire to feed because digestive enzymes are significantly affected by the temperature, even in goldfish aquariums. Sudden changes can cause stress and lead to disease.


For goldfish and other cold-water fish, such as Medakas and White Cloud Mountain fish and some North American midgets like the pygmy sunfish, no extra heat is necessary. For most tropical fish which include the South American, Mexican and Asiatic fishes, temperatures never lower than 70 degrees are needed.

Unless you live in a very warm climate or keep your house very warm, it will be difficult to achieve this ideal temperature without the help of an aquarium heater. Not only will an aquarium heater warm your tank water to the right level, but it will also prevent sudden fluctuations in temperature.

Most aquarium heaters allow you to set a goal temperature or temperature range for maintenance – the heater turns off when the tank temperature is within that range and turns on when it drops too low. For some types of aquariums, the heater is an essential part to keep the fish healthy and happy in their own environment.

How To Use An Aquarium Heater?

Although most tropical fish can be kept between 75 to 80 °F, it is recommended to ensure that species are kept at their optimal range. This should be considered when selecting fish for a community aquarium.

Aquariums housing large fish should always use a heater guard or place the heater where accidental breakage is unlikely.

Rules for handling with a fish tank heater

  1. Placement

    Placing the heater in an area where there is good water movement will help distribute heat efficiently.

  2. Use it only under water

    Do not switch your heater on unless the heating element is immersed in water, otherwise, it will overheat and break.

  3. water level

    If you have a submersible heater, be careful to water loss due to evaporation and ensure that the water level is always higher than the heater.

  4. temperature equilibrium

    Before plugging the heater in, allow it immersed in the aquarium water at least 30 minutes to give it a time to reach temperature equilibrium and prevent the glass from breaking.

  5. Unplugging

    Similarly, always wait at least 30 minutes after unplugging if you want to remove it out of your aquarium.

  6. Water temperature

  7. It’s recommended to fill the aquarium with water that is close to your desired aquarium temperature.

  8. Safety first

    Always unplug your heater if you must place your hands in the aquarium for safety.

  9. Check temperature daily

    Do Always set temperature with the use of an aquarium thermometer and verify temperature on a daily basis.

A common misconception is that of unplugging the heater during warmer weather. This should not be done because the heater maintains aquarium temperature stability by not allowing aquarium temperature to drop down its setting and is thermostatically controlled.

If you have trouble with your tank temperature being consistently too high, you may need to invest in an aquarium chiller, not a heater.

You may like: How to set up a submersible aquarium heater?

Affiliate links & Images from Amazon Product Advertising API. Last update on 2022-09-11.

Top Editor's Choice on Aquarium Heater

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Tetra Whisper Easy to Use Air Pump for Aquariums (Non-UL)
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Loctite Tite Foam Big Gaps White Insulating Foam Sealant, 12 oz, 1, Can
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SaleBestseller No. 8
Ecosmart ECO 8EcoSmart 8 KW Electric Tankless Water Heater, 8 KW at 240...
The product is highly durable; The product is easy to use; Manufactured in China; Heating elements are durable and are threaded for easy replacement
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Kasa Smart HS100 WiFi Smart Plug, Classic 1-Pack, White
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