Beautiful planted tropical freshwater aquarium with fishes

Best 20 Gallon Fish Tank Heater: Review and Buyer’s Guide (2022)

Fish are unable to control their own body heat, so heater is necessary in most home aquariums, particularly those that house tropical or marine species.

However, choosing a 20-gallon fish tank heater can be a bit stressful due to the huge number of things you need to consider, such as the unit’s wattage, temperature range, and durability.

  • Comes with an external controller 
  • Includes two suction cups
  • LED temperature display and built-in thermometer 
  • Made from durable, shatterproof glass
  • Nickel-chromium alloy heating alloy
  • Sturdy suction cups
Best Value
  • Includes a thermal switch 
  • High-quality heating core
  • Comes with a mounting bracket with 3 viewing windows
Editor’s Choice

As someone who has been keeping fish for over a decade, I know exactly what to look for when selecting a heater for a 20-gallon aquarium.

So, to save you a bit of time and confusion, I’ve compiled a list of the best heaters for 20-gallon tanks to help you decide on the right aquarium heater for your fish and setup.

The Best From The Reviews

Top Pick

Hygger 100W Mini Submersible Digital Display Aquarium Heater

Out of all the aquarium heaters I’ve looked at for a 20-gallon tank, this one is my top selection.

Hygger 100W Mini Submersible Digital Display Aquarium Heater

This 100-watt submersible fish tank heater from Hygger boasts a compact, oval design, and includes an external controller to easily adjust the temperature of the unit. It comes with two suction pads, a built-in thermometer, LED display, and indicator lights.

Best Value

DaToo Submersible Aquarium Heater

This is the best heater for 20-gallon tanks that’s both affordable and constructed to a high standard.

DaToo Submersible Aquarium Heater

The DaToo Aquarium Heater is hard to beat in terms of efficiency and affordability. It features a shatterproof, durable glass exterior and high-quality heating core for even heat output. 

Editor’s Choice

Marineland Precision Heater

Despite its slightly higher price tag, this heater is high quality and comes with a range of useful features, making it my personal favorite to use for a fish tank.

Marineland Precision Heater

Suitable for both 20-gallon freshwater tanks and saltwater tanks, the Marineland Precision Heater is a great pick for your tank as it has a superior heating element for even heat distribution, alongside other features like a mounting bracket.

On To The Reviews…

Top Pick

Hygger 100W Mini Submersible Digital Display Aquarium Heater

The Hygger 100W Mini Submersible Aquarium Heater is ideal for 20-gallon tanks as it’s powerful, reliable, and comes with useful features like a built-in thermometer, external controller, indicator lights.

Hygger 100W Mini Submersible Digital Display Aquarium Heater

First up is the Hygger 100W Mini Aquarium Heater, featuring a compact and oval shape design. Due to its small size (it’s only 2.76″ x 1.38″ x 4.53″!), the unit won’t take up too much space in your aquarium, which provides your fish with more swimming space,

External Controller

It comes with an external controller with a wide water temperature range, allowing you to easily adjust the temperature of the unit without getting your hands wet.

LED Display and Light Indicators

The front side of the heater has a bright LED display so it can be viewed in dark environments.

I like that the submersible heater has a light to let you know when the unit is actively heating as this alerts you to any issues with the device. A few years back, my heater stopped working for a few days without me knowing, which led to a few casualties in my fish tank.

Having an indicator on my heater would have informed me earlier of the malfunction and potentially saved the lives of some of my aquarium fish!

Built-In Thermometer

The Hygger 100W Aquarium Heater also has a built-in thermometer so you can keep an eye on the water temperature of your aquarium, as well as strong suction cups on the back of the unit that can lock onto acrylic, plastic, and glass tanks.

Auto Shut Off

Another feature I like about this aquarium heater is its ability to turn off once the desired temperature has been met. This prevents the device from overheating your aquarium so your fish don’t get too hot.

The only issues I’ve found with this submersible heater from Hygger are its slight noisiness and occasional inaccuracy. The unit can emit a mild buzzing/humming sound and the thermometer can sometimes display a different temperature than the actual warmth of the aquarium. 

This is only by a degree or two, so it’s not a huge issue, but you might want to consider using a separate thermometer to be on the safe side. See my review of the best aquarium thermometers and find the ideal thermometer for your tank.

Specs

  • Product Dimensions: 2.76" x 1.38" x 4.53"
  • Product Weight: 9.59 oz
  • Wattage: 100 W

Pros

  • Compact design
  • Adjustable temperature via an external controller
  • Built-in thermometer
  • LED display and indicator light

Cons

  • Unit can be a little noisy
  • Thermometer can be inaccurate

Best Value

DaToo Submersible Aquarium Heater

The DaToo Aquarium Heater is made from shockproof, heavy-duty, and shatter-resistant microcrystalline glass, ensuring its longevity and safety. It has a wide temperature range, thermostat system, and sturdy cups for suction.

DaToo Submersible Aquarium Heater

If you need a top-quality heater for your 20-gallon fish tanks that’s also budget-friendly, look no further than the DaToo Submersible Aquarium Heater. It’s rated 100 watts and is made from durable, shatterproof, and shock-resistant microcrystalline glass.

Adjustable Water Temperature Dial

There’s an adjustable water temperature dial on the top of the unit with a range from 68° F to 93 ° F, so it’s ideal for freshwater tanks and saltwater aquariums. The heating core is made of nickel-chromium alloy for even heat distribution, preventing any cool or hot spots in your tank.

It comes with an electronic thermostat system and suction cups, the latter of which stick to all tank surfaces with ease.

BPA-Free Plastic Components

I also like that the plastic components in the unit are made from durable, BPA-free plastic to ensure the safety of your fish.

My only gripe with this heater is its short power cord (it’s only around 3.3 feet!). You might need to use an extension cord with the device unless your power outlet is positioned close to your tank.

Specs

  • Product Dimensions: 11.2" x 2.8" x 1.7"
  • Product Weight: 8.01 oz
  • Wattage: 100W

Pros

  • Made from high-quality, shatterproof microcrystalline glass
  • Adjustable, precise temperature control
  • Thermostat system
  • Heating core allows for even heat distribution

Cons

  • Power cord is a little short

Editor’s Choice

Marineland Precision Heater for Saltwater or Freshwater Aquariums

This 100-watt submersible heater from Marineland sports a dial that can be adjusted to make changing the warmth of your tank easy. It comes with a mounting bracket with 3 windows for hassle-free installation.

Marineland Precision Heater for Saltwater or Freshwater Aquariums

If you can afford to spend a little extra on a heater for a 20-gallon tank, I fully recommend the Marineland Precision Heater due to its effectiveness and durability. The company is well-known for their first-rate aquarium products, and this heater is no different!

I’ve used a variety of aquarium heaters and filters from Marineland in my tanks and I can’t fault them – they’re fantastic quality.

Adjustable Temperature Dial

The heater wattage is 100W, so it’s plenty powerful enough for a 20-gallon tank. It has a temperature dial that can be adjusted so you have full control of the warmth of your aquarium water.

Thermal Switch

The thermal switch automatically turns off as the temperature rises above the device’s internal preset. If the temperature in your tank drops, the heater automatically turns back on, too!

Even Heat Transfer and Improved Durability

The heating core contains a mica core which is surrounded by a mesh heating component, allowing for even heat transfer and improved durability, so the unit should last you a considerable amount of time.

Easy Installation

To make the submersible heater easy to install in your aquarium, it comes with a mounting bracket that has 3 window positions. This lets you clearly see the temperature display, which is a feature I really like.

However, this Marineland heater doesn’t always heat consistently – the stated temperature on the unit isn’t always the actual water temperature of your aquarium.

I’d suggest using a separate thermometer to check the temperature of your tank to be on the safe side.

Specs

  • Product Dimensions: 3.94" x 1.63" x 11.63"
  • Product Weight: 9.76 oz
  • Wattage: 100 W

Pros

  • Automatically turns off when the desired temperature is met
  • Adjustable temperature range to make setting temperature easy
  • Comes with a mounting bracket

Cons

  • Doesn’t always heat consistently

Aqueon Preset Heater

The Aqueon Preset Heater is a convenient device as its set temperature is 78° F, which is ideal for most tropical species. It’s shatter resistant and has an LED light to indicate when it is actively working.

Aqueon Preset Heater

Another solid heater for a 20-gallon tank is the Aqueon Preset Aquarium Heater, a fully submersible 100-watt device that automatically shuts off when it overheats and resets once it’s cooled down.

Shatter Resistant

The heater is shatter resistant for safety and features an LED light that turns on when the unit is actively heating.

Suitable For Most Tropical Fish

I like this heater as it’s preset to 78° F, which is suitable for most tropical fish, as this removes the hassle of adjusting the water temperature to find the ideal warmth for your tank.

However, if the species you keep need a higher temperature than 78° F like freshwater angelfish (best kept at water temperatures between 78° F to 84 78° F, then one of the fish tank heaters I’ve looked at above might be a better option.

The only downside of this heater for 20-gallon tanks is its slight lack of power. The unit can struggle to heat reliably as it often falls a few degrees short of 78° F. If your fish prefer cooler water temperatures, then this isn’t a huge issue for an otherwise solid heater.

Specs

  • Product Dimensions: 3.5" x 1.5" x 7.75"
  • Product Weight: 8 oz
  • Wattage: 100W
  • Full Specs

Pros

  • Preset to 78° F
  • Shatter resistant
  • LED light to let you know when unit is heating

Cons

  • Can be a bit unreliable

Orlushy Submersible Aquarium Heater

This fully submersible glass aquarium heater from Orlushy features an external thermostat, suctions cups, and a study quartz glass construction.

Orlushy Submersible Aquarium Heater

Next up is the Orlushy Submersible Heater, which is rated 100 watts. It boasts a 6-foot power cord and 2mm thickened quartz glass construction that’s explosion proof.

Accurate and Easy to Use

The water temperature dial can be adjusted from 68 to 89° F, giving you full control of your aquarium climate. It’s easy to use and can be changed in small intervals to ensure accuracy.

Maintains a Stable Temperature

My favorite feature of this 20-gallon tank heater is its sensitive and reliable thermostat as it maintains a stable temperature. I also like that the unit automatically turns off once the set temperature has been reached.

Suction Cups for Easy Installation

The unit comes with suction cups for quick and easy installation too!

Unfortunately, the suction cups included with this submersible glass aquarium heater from Orlushy are a little flimsy, making them prone to tearing. You can purchase suction cups for heaters separately, so this issue is easy to fix.

The thermostat can also sometimes be a bit inaccurate, so I’d advise using a separate digital thermometer with this heater.

Specs

  • Product Dimensions: 10.79" x 3.58" x 13.76"
  • Product Weight: 13.76 oz
  • Wattage: 100W

Pros

  • Explosion-proof quartz glass construction
  • Wide temperature range
  • Automatic shut-off to prevent overheating

Cons

  • Suction cups can tear easily
  • Thermostat isn’t always accurate

EHEIM Jager Aquarium Thermostat Heater 100W

Featuring a shatterproof and shock-resistant design, the EHEIM Jager Aquarium Heater maintains accurate temperature settings and automatically turns off when the water level in your tank falls too low.

EHEIM Jager Aquarium Thermostat Heater 100W

The last heater I recommend for a 20-gallon tank is the EHEIM Jager Aquarium Thermostat Heater, sporting a shatterproof and shock-resistant quartz glass construction.

Thermo Safety Control

I appreciate that the unit has a thermo safety control to protect it against running dry as this prevents it from breaking if it’s left out of the water for a short period of time. I also like that it has a TruTemp dial to recalibrate the device to ensure its preciseness and accuracy,

Auto Shut Off

This fully submersible heater has an auto shut off feature, it automatically turns off when the water level drops too low, which is another useful feature. It also has an on/off indicator to help you monitor its efficiency and effectiveness.

However, this aquarium heater for a 20-gallon tank can be a bit difficult to calibrate, but once you’ve completed the process, the unit maintains the perfect temperature.

Specs

  • Product Dimensions: Not Specified
  • Product Weight: Not Specified
  • Wattage: 100W

Pros

  • Shatterproof and shock resistant
  • Turns off when the water level drops too low
  • On/off indicator

Cons

  • Can be hard to calibrate

Do 20-Gallon Aquariums Need a Heater?

To help you decide on the best heater, let’s discuss why it’s needed and the qualities you should look for.

A Reef Aquarium with Fish
Fish Swimming in a Reef Tank

A 20-gallon tank will need a heater if it’s stocked with tropical fish or invertebrates to ensure the water temperature doesn’t drop too low. Most tropical species do well at temperatures around 78° F, but some specimens may require cooler or hotter temperatures. 

An aquarium heater also keeps the tank water at a consistent warmth throughout the day, ensuring it doesn’t drop too low during the evening or cooler weather. If you live in a cold climate, it’s important to use an aquarium heater in your tank as the ambient temperature will be far too low for tropical fish.

NOTE

You may need to use a heater even if you own coldwater species if you’re from a particularly chilly climate or regularly experience cold weather.

What Is the Best Heater for a 20-Gallon Fish Tank? 

The best heater for 20-gallon tanks is a 100-watt unit as this will be powerful enough to heat most aquariums of this volume. It should be shatterproof, shock-resistant, and ideally come with suction pads or a mounting bracket so it can be installed horizontally or vertically.

The best aquarium heaters come with an LED indicator to let you know when the device is actively working, alongside an electronic thermometer or thermostat so you can check the thermometer of the device.

It Depends on the Type of Fish

Depending on the type of fish you own and their preferred temperature range, you might want to use a device with adjustable temperature settings to ensure your tank water is at an appropriate warmth.

Although devices with a preset temperature are convenient as you don’t need to manually adjust them, that also means your aquarium can only be heated to the preset temperature – no more, no less.

If your fish require a warmer or cooler temperature, then a preset heater might not be the best choice for you.

TIP

Some heaters come with a heater guard to protect your fish from burns if they touch the device. If your heater doesn’t include a heater guard, I’d recommend purchasing one separately (don’t worry, they’re pretty inexpensive!) to keep your fish safe.

Types of Aquarium Heaters

Fish Tank Being Filled with Water
Fish Tank Being Filled with Water

There are a few different types of heaters for 20-gallon tanks, each with their pros and cons. I’ll be explaining about each type of tank heater below and how they work to help you select the right unit for your aquarium.

Hanging/Immersible Heaters

A hanging heater goes over the top of your tank, with the heating component placed inside your aquarium to increase the warmth of your aquarium.

Substrate Heaters

A substrate heater is normally paired with a second heater and consists of a long heating wire that is attached to the bottom of your tank (under your substrate). Substrate heaters are ideal for planted tanks as they increase water movement in the substrate to encourage plant growth.

Submersible Heaters

Submersible heaters are the most common type of heater used in aquariums. These heaters are designed to be fully submerged and are usually constructed out of glass tubes (sometimes titanium) with a coiled heating element inside.

This type of heater should always be fully submerged

Submersible glass heaters are at risk of shattering, especially if they are placed out of water without being switched off and left to cool down. This type of heater should always be fully submerged to prevent damage to the unit.

Filter Heaters

A filter heater is essentially a filtering system that comes with a built-in heater. This type of device heats up the water as it is filtered through the filter.

In-Sump Heaters

In-sump heaters are heaters that go inside your aquarium sump, which is a small tank that is placed beneath your main setup. Sumps are commonly used to house filtration for your main tank.

In-Line Heaters

An in-line heater is placed on the outflow line of your filter to allow it to warm up the water that is pumped back into your tank. This heater type is best for large or aggressive fish that are prone to damaging aquarium equipment.

What Size Heater for a 20-Gallon Fish Tank?

The right size heater for a 20-gallon tank is 100 watts as the general rule when calculating the correct size heater for a tank is 5 watts per gallon of water.

Multiple Heaters

If your heater wattage is below 100W, you may need to use more than one heater to ensure your tank water is at an appropriate warmth. For instance, you can use a couple of 50-watt fully submersible aquarium heaters in a 20-gallon tank.

Here’s a video to help you choose the ideal heater for your fish tank…

How to Choose an Aquarium Heater

How Long Does It Take to Heat Up a 20-Gallon Fish Tank?

How long it takes to heater a 20-gallon tank depends on the wattage of your heater, the ambient temperature of your aquarium, and the type of heater you’re using. That being said, most heaters will take around 24 to 36 hours to fully heat a 20-gallon tank.

Final Thoughts

I hope I helped you find the best heater for 20-gallon tanks and what to look for when choosing the right heater for your tank.

If you’re still a little undecided, here’s a quick rundown of my top recommendations.

  • Comes with an external controller 
  • Includes two suction cups
  • LED temperature display and built-in thermometer 
  • Made from durable, shatterproof glass
  • Nickel-chromium alloy heating alloy
  • Sturdy suction cups
Best Value
  • Includes a thermal switch 
  • High-quality heating core
  • Comes with a mounting bracket with 3 viewing windows
Editor’s Choice

Top Pick

The Hygger 100W Mini Submersible Heater features a compact design so it doesn’t take up too much space in your tank. It has an external controller to make adjusting the temperature range of the device easy, as well as a digital thermometer, LED indicator light, and bright LED display.

Best Value

If you need a practical but inexpensive 20-gallon fish tank heater for your tank, the DaToo Submersible Heater is the best aquarium heater for the job. It’s shockproof, durable, shatter-resistant, and includes a temperature control, suction cups, and thermostat.

Editor’s Choice

Finally, if you can afford to spend a bit extra on submersible heaters, the Marineland Heater is well worth considering. It heats evenly and has a wide temperature range, as well as extra features like a mounting bracket.

Feel Free To Share!

Which heater did you choose for your tank? Be sure to let me know on our social media platforms and share this article with other aquarists so they can find the best heaters for their 20-gallon aquarium.

If you need more advice on fishkeeping, take a look at our other guides here. In case you need a filter or a hood for your 20 gallon tank, Here’s the Best 20-Galllon Fish Tank Filter review and the Best 20 Gallon Aquarium Hood review.

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Mollie Newton
Mollie Newton
Founder of PetMeTwice. I love all types of animals from fish to fluff-balls! I also enjoy writing short stories and helping train animals 🤩