Most freshwater fish come from tropical environments and thus require an aquarium heater to maintain the water temperature in the mid- to high-seventies or low-eighties. With or without tropical fish in your tank, a heater with a quality thermometer will also help to control and prevent the temperature changes in your fish tank that cause stress and harm for your fish. In this review, we will provide you some of the best aquarium heaters for tanks from small 1-gallon tanks to extra-large ones. Besides, we also provide you some tips to choose the right heater as well as how to use them in the right way.

Types of aquarium heaters

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 in 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.


Submersible aquarium heater

In-line aquarium heater is one that is inserted into the return hose of a filtration system (canister filter, wet/dry filter…). 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.

Hydor In-Line external heater, 300W, 5/8-inch hoseHydor In-Line external heater, 300W, 5/8-inch hose

Another type is Hang-On controller with heating tube. It includes two component: a digital 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. Aquarium heater controllers with heating tube are usually designed with high wattages for large aquariums. They are ideal to keep an optimal temperature for large to extra-large fish tanks.

Finnex Hang-On electronic controller aquarium heaterFinnex Hang-On electronic controller aquarium heater

Choosing the right heater by your tank 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 25 watt 50 watt 75 watt
10 gal/50 L 50 watt 75 watt 75 watt
20 gal/75 L 50 watt 75 watt 150 watt
25 gal/100 L 75 watt 100 watt 200 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: I position my 20 gallon aquarium in a room that has an ambient temperature of 68 degrees Fahrenheit and my desired aquarium temperature is 77 degrees Fahrenheit. That means I need to heat 20 gallons of the aquarium water a temperature of 9 degrees Fahrenheit. Based on the previous table, a 50-watt heater is perfectly fit for my tank.

Best aquarium heater reviews

Marina Betta submersible heater for Betta tanks up to 1.5 gallons

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 small size tanks up to 1.5 gallons.

The heater is automatic to create an ideal water condition for your Betta to thrive in. It is designed to reach and maintain a set temperature without manual adjustments required. A red indicator light will illuminate to help you know when the heater is working. A suction cup is also included for you to install the heater in the right place inside your tank.

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Hydor Slim heater 7.5 W for 2 – 5 gallon Betta tanks, bowls

  • Hydor Slim Heater for Bettas, Bowls and AquariumsEditor's rating: Check on
  • Model: Hydor Slim heater for Betta tanks, bowls
  • Type: submersible
  • Wattages: 7.5 W
  • Ideal for 2 – 5 gallon Betta aquariums or other small tanks.

Like the previous, this is also a good small fish tank heater that you can use on your 2 – 5 gallon fish tanks or bowls. Only plug and play without any adjustments needed, the heater will do its work to keep your tank temperature ideal for fish.

Aqueon Pro heater, 50 – 250W for 10 – 75 gallon aquariums

  • Aqueon Pro HeaterEditor's rating: Check on
  • Type: fully submersible
  • Wattages: 50W, 100W, 150W, 200W, 250W
  • Temperature reading: Fahrenheit
  • Used for: both saltwater or freshwater
  • Special features: electronic thermostat for accurate temperature settings, indicator light, nearly indestructible.
  • Return to the previous guide to know which wattage fits your tank.

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 very easy for you to use the heater, only rotate the temperature adjustment knob on the top of it to set your desired one. There are many sizes from 50 to 250 watts for aquariums from small to large. While the 50W heater is ideal for a 10 gallon fish tank, the 250W can be used for aquariums up to 75 gallons.

Finnex Digital Heater Controller with Deluxe Titanium Tube

  • Finnex Digital Heater Controller with Deluxe Titanium TubeEditor's rating: Check on
  • Type: heater controller with heating tube
  • Temperature reading: Celsius & Fahrenheit
  • 300W heating tube for 40 – 80 gallon tanks
  • 500W heating tube for 70 – 130 gallon tanks
  • 800W heating tube for 140 – 265 gallon tanks
  • Special features: audio alert system

Featuring an advanced technology, the Finnex Digital heater is sold as a combination of a 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.

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 installation.

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Tetra HT submersible aquarium heater, cheapest and affordable

Tetra HT submersible heaters are fairly cheap; however, they are capable of maintaining a water temperature at a constant level to protect your aquarium inhabitants from temperature fluctuations. They are very cheap, so buying them if you are on a budget. There are three available wattages for you to choose.

EHEIM Jager aquarium thermostat heater, 25 – 300 W

  • EHEIM Jager Aquarium Thermostat HeaterEditor's rating: Check on
  • Type: submersible.
  • Wattages: 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).
  • Used for: both saltwater or freshwater.
  • Special features: protect against running dry, on/off indicator light, made of shock resistant and shatter proof glass.

This EHEIM Jager heater features an innovative TruTemp technology with a readjustment ring that allows you to adjust the heater to your precise desired temperature. There is an on/off indicator light which indicates when the heater is working. Another unique feature is the thermo-safety control, which automatically switches off the heater when out of the water, hence protecting it from the damage of running dry.

The heater is made of rigid special laboratory glass, which is shockproof and shutter-resistant. It is fully waterproof, fully submersible and UL-approved. There are many sizes for different tank sizes up to 264 gallons. It comes with suction cups for easy installation.

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Fluval E Electronic heater, most accurate for large fish tanks

  • Fluval E Electronic heaterEditor's rating: Check on
  • Type: submersible
  • Wattages: 100W, 200W, 300W.
  • Used for: both freshwater or marine tank.
  • The 100-watts used for aquariums up to 30 gallons
  • The 200-watts used for aquariums up to 65 gallons
  • The 300-watts used for aquariums up to 100 gallons
  • 5 year warranty.

This is one of the most accurate heaters in the market manufactured by Fluval. It uses dual temperature sensors to provide an accurate temperature range for your aquarium. Moreover, it owns most advanced features of a modern heater such as LCD temperature display available in both Fahrenheit and Celsius, fast heat technology built with a safety shut-off, integrated fish guard, colored display alert system, slim profile mounting bracket.

Aquatop Quartz Glass submersible heater (50 – 300W)

  • Aquatop Quartz Glass submersible heaterEditor's rating: Check on
  • Type: fully submersible
  • Wattages: 50W, 75W, 100W, 150W, 200W, 250W, 300W
  • Temperature reading: Celsius & Fahrenheit
  • Used for: both saltwater or freshwater.

Aquatop Quartz Glass submersible heater is made from high quality insulated glass with double insulation for added safety and durability. It offers a visible temperature setting ranging from 68 to 93 degrees Fahrenheit (20-34°C). There is a temperature adjustment knob on the top for you to easily set your desired temperature. It is suitable for both saltwater and freshwater tanks and very easy to install with the use of provided suction cups.

Best aquarium thermometers for your fish tank

You should buy the best aquarium thermometer to control the temperature of your aquarium water if the heater doesn’t come with anyone. Thermometers exist in a variety of styles and attach to either the inside or outside of the aquarium. They are needed once adjusting the heater to the desired temperature or verifying the setting on a daily basis.

Zacro LCD Digital aquarium thermometerZacro LCD Digital aquarium thermometer HDE Digital aquarium thermometerHDE Digital aquarium thermometer AODE® Digital LCD aquarium thermometerAODE® Digital LCD aquarium thermometer

For small fish tanks with Bettas or other small tropical fish, these following thermometer will work well for the money.

Marina floating thermometer with suction cupMarina floating thermometer with suction cup American thermal instruments aquarium thermometerAmerican thermal instruments aquarium thermometer

Inexpensive stick-on thermometers, which can be attached to the outside of the tank, are 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.

SunGrow Fast-Read thermometerSunGrow Fast-Read thermometer Stick on themormeterStick on themormeter

Do your fish tank need a heater?

Fish are cold blooded like reptile and they maintain the same body temperature as their environment. It is extremely important to maintain constant temperatures. 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 pigmy 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, 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 oF, 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:

  • Placing the heater in an area where there is good water movement will help distribute heat efficiently.
  • Do not switch your heater on unless the heating element is immersed in water, otherwise, it will overheat and break.
  • If you a submersible heater, be careful to the water loss due to evaporation and ensure that the water level is always higher than the heater.
  • 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.
  • Similarly, always wait at least 30 minutes after unplugging if you want to remove it out of your aquarium.
  • It’s recommended to fill the aquarium with water that is close to your desired aquarium temperature.
  • Always unplug your heater if you must place your hands in the aquarium for safety.
  • It is recommended to use warm water that has temperature close to your desired temperature to fill the tank.
  • 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.

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