The Best 20 Gallon Aquarium (2024 Buyer’s Guide)

20 gallon fish tank on a desk
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: April 9, 2024
Review Process and Evaluation Criteria
We conduct hands-on testing for all the products highlighted in our reviews and guides. Through anonymous product ordering and involving an independent team of testers, we gather direct experience to offer recommendations backed by data.

A 20-gallon aquarium is an exceptional option for both beginner and experienced aquarists due to its comparatively simple maintenance when compared to larger tanks. Furthermore, it’s a spacious tank that can house a diverse range of colorful fish, not to forget unique aquatic animals like axolotls.

However, when choosing the best 20-gallon aquarium, there’s a lot that you need to consider, including the quality of the tank, its durability, and whether it comes with any features or accessories you need for your freshwater or saltwater setups.

Article Summary

  • A 20-gallon aquarium is a versatile size suitable for both beginner and experienced aquarists, offering ease of maintenance and a decent size for various fish species and exotic pets.
  • The top recommendations are the Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit, Marina LED Aquarium Kit, and Aqueon Aquarium Starter Kit with LED Lighting.
  • Consider the size and bioload of your fish when determining how many fish to keep in a 20-gallon tank, following the rule of 1 inch of fish per 1 to 2 gallons of water.

As someone who’s been in the fishkeeping hobby for over a decade, I’ve been through my fair share of freshwater tanks, saltwater tanks, reef tanks, and planted tanks (both good and bad!), so I know what to look for when it comes to deciding on a 20-gallon fish tank.

To help you find the right 20-gallon tank for your needs and budget, I’ve compiled a list of some of my top recommendations.

The Best From The Reviews

Top Pick

Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit

This 20-gallon Tetra kit comes with all the accessories you need for your new tank, including a filtration unit, heating device, LED hood, and even plastic plants.

Top Pick: Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit

Out of all the tanks I’ve looked at, this one is my top pick due to its quality and wide range of accessories.

Best Value

Marina LED Aquarium

This 20-gallon tank kit features a strong glass construction and comes with a huge range of accessories, including a filtration unit, LED light hood, fish food, water dechlorinator, and more.

Best Value: Marina LED Aquarium

This fish tank is my top recommendation for aquarists looking for a great-quality tank on a budget.

Editor’s Choice

Aqueon Aquarium Starter Kit with LED Lighting

The Aqueon Aquarium Starter Kit is a fantastic tank for new fish owners as it includes basic equipment like a heater and filtration system, as well as other goodies such as fish food and a fish net.

Editor’s Choice: Aqueon Aquarium Starter Kit with LED Lighting

Although a little costlier than some of the other tanks I’ve looked at, this tank more than makes up for in features and quality.

On To The Reviews…

Top Pick

Tetra ColorFusion 20 Gallon Aquarium

The Tetra ColorFusion Kit comes with everything you need to start keeping fish, including a 20-gallon tank, filtration unit, heater, LED light, hood, and plastic plants.

Top Pick: Tetra ColorFusion 20 Gallon Aquarium

The Tetra ColorFusion is a fantastic 20-gallon tank, especially if you’re new to fish keeping due to the huge number of extras it comes with. The tank itself is sturdy and durable, ensuring the security and safety of your fish.

There’s a tank hood included with the aquarium kit, which is useful for species with a tendency to jump or escape from their habitat, such as betta fish and amano shrimp.


I also like that the aquarium kit comes with a fish tank heater to keep your tank temperature stable, HOB (hang-on-back) filter, and color-changing LED lights, all of which are the bare essentials any tank for tropical fish should contain.

My favorite feature of this Tetra tank is the color-changing LED lights it comes with, which are known to be excellent in performance and energy conservation. Both artificial and live plants look spectacular under each of the different hues (it features all the colors of a rainbow!).

The light also works to enhance the colors of your fish, making them look more visible and vibrant.

Artificial Plants

If that wasn’t enough, this Tetra aquarium kit also includes a couple of fake plant multipacks and an artificial white anemone to liven up your tank and provide your fish with enrichment.

While the tank in this kit is of excellent quality, the same can’t be said with some of the included accessories.

The filtration unit can be a little noisy and lack power, so it may be unsuitable for larger species such as goldfish. Additionally, the fish tank heater is a piece of low-quality equipment that can break prematurely.

Fortunately, both of these two pieces of tank equipment are relatively inexpensive, so you can purchase them separately. Despite its faults, I still think this kit from Tetra is a solid choice, particularly for less demanding or small aquatic creatures.


  • Product Dimensions: 27.88” x 16.33” x 20.38”
  • Product Weight: 34.6 lbs
  • Shape: Rectangular


  • Sturdy and durable tank
  • Comes with a variety of accessories like a filter, heater, and light
  • Included LED light helps enhances the colors of live plants and fish


  • Some of the included accessories aren’t the best quality
Best Value

Marina LED Aquarium Kit

This 20-gallon fish tank provides you all the equipment and accessories you require to get started in the fish keeping hobby, such as fish flakes, water conditioner, a filtration unit, LED hood, fish net, and biological supplement.

Best Value: Marina LED Aquarium Kit

If you’re looking for a great 20-gallon fish tank that won’t break the bank, I fully recommend the Marina Aquarium Kit. Not only is it affordable, but it also comes with everything you need for keeping fish.

The tank itself sports a sleek design and high-quality glass construction, providing your fish with a safe and attractive habitat to call home.


I like the huge variety of equipment included with the kit, such as a clip-on filter, filtration cartridges, and LED hood with a natural daytime effect.

The filtration unit is relatively quiet so you can enjoy your tank without any distractions. I also appreciate that the light is built into the hood for convenience and to reduce installation time.

Extra Goodies

Alongside a filter and LED hood, you get many other goodies included in the kit like premium fish food (Fluval Max Fish Food) that fish love, water conditioner (to make your tap water safe), and a net (made from soft mesh to protect fragile fins!).

You even get a biological supplement to boost beneficial bacteria colonies in your tank water, and a handy care guide to help you correctly set up your tank.

As much as I like this fish tank, I found that the included filter is a little lacking in power for the tank size. I’d advise purchasing a separate 20-gallon filter to keep your tank clean, ideally one with a water flow rate of at least 80 GPH (gallons per hour).


  • Product Dimensions: 24” x 12.5” x 16.5”
  • Product Weight: 35 lbs
  • Shape: Rectangular


  • Tank features a sleek and sturdy glass construction
  • Includes a filtration unit and hood with built-in LED lighting
  • Comes with accessories such as fish food, water conditioner, and a fish net


  • Included filter isn’t powerful enough for the tank size
Editor’s Choice

Aqueon Aquarium Starter Kit with LED Lighting

This tank from Aqueon boasts a high-clarity design and comes with a wide assortment of accessories to keep your fish happy and healthy, including a heater, filter, LED light, fish flakes, and much more.

Editor’s Choice: Aqueon Aquarium Starter Kit with LED Lighting

One of my personal favorite 20-gallon aquariums is the Aqueon due to its crystal clear design and huge selection of extras. I’ve used many Aqueon products during my time as a fishkeeper and I can’t fault them – they’re one of my top brands.

Good For Beginners

This tank comes with everything a beginner aquarist needs to get started, including a hood with built-in cool white LED lighting for a natural ocean feel, a QuietFlow power filter, filtration cartridge, preset heater, water dechlorinator, fish flakes, fish net, stick on thermometer, and a setup guide.

The size of the tank and the included features make it a good choice for both saltwater tank and freshwater aquarium setups. I like that the heater is preset to a constant 78 degrees (ideal for most tropical species of fish) for convenience.

LED Light

The filtration unit also features a red LED light that flashes to let you know when you need to replace the filter cartridge, which is useful for keeping your tank water clean and healthy.

My only concern with this tank is that the LED light can be prone to moisture build up because it doesn’t come with a splash guard. It might be worth purchasing one of these equipment separately to keep the light dry and maintain its efficiency.


  • Product Dimensions: 24.25” x 12.5” x 19.5”
  • Product Weight: 32.25 lbs
  • Shape: Rectangular


  • Crystal clear design
  • Includes a filter, heater, and light
  • Comes with extras such as a net, food sample, and water dechlorinator


  • LED light is prone to moisture build up

Aqueon Aquarium 20 Gallon Long

The Aqueon 20-gallon tank sports a stylish, clear design and sturdy construction, making it a great option for aquarists who need a dependable enclosure for their fish.

Aqueon Aquarium 20 Gallon Long

Next up is this 20-gallon long tank from Aqueon, sporting an attractive design and clear glass construction. It has a stylish black trim along the top and base of the tank, as well as durable silicone edges to prevent leaks.

Leak Prevention

One of my old tanks used to leak frequently due to poor-quality silicone edges – at least once a week, I’d need to pull out my fish tank silicone to reseal it.

If I’d purchased a more heavy-duty and secure enclosure like this one, it would have saved me a lot of time and money!

My only gripe with this fish tank is its price tag, which is a little on the higher end, at least compared to some of the other rectangular tanks I’ve reviewed. However, I still think it’s a good standard glass aquarium for fish keepers who need something simple but practical.


  • Product Dimensions: 30.25” x 12.5” x 17.5”
  • Product Weight: 22 lbs
  • Shape: Rectangular


  • Sturdy glass aquarium
  • Secure silicone edges
  • Attractive black trim


  • Bit pricey

GloFish Aquarium Fish Tank Kit

The GloFish Fish Tank Kit offers a colorful and healthy environment for your fish. Alongside a strong tank, you get a filtration unit, heater, light, lid, and a few other extras.

GloFish Aquarium Fish Tank Kit

Another great 20-gallon fish tank is this stater kit from GloFish, which comes with a sturdy tank and a good selection of colorful extras. I like that the tank is made from scratch resistant glass as this helps ensure its durability and longevity.

LED Tank Hood

The kit comes with an LED tank hood to illuminate your tank and keep your aquatic friends safe, as well as a quiet but dependable filtration unit with a reliable filter current.

You get a Tetra mini UL heater to keep your tank water at the ideal temperature for fish that originate from warm climates, alongside a gorgeous submersible LED light stick that produces a shimmery blue effect.

Artificial Plants

If the latter wasn’t colorful enough for you, the GloFish kit includes a multipack of fluorescent fake plants and a bright GloFish yellow anemone to really make your tank stand out.

Last but not least, a water dechlorinator, food sample, and setup guide are included with the kit, so the only things you need to purchase separately are substrate and fish!

The main downside of this GloFish tank is the flimsy hood. It doesn’t fit the tank properly, causing it to slip down or fall inside the enclosure frequently. I’d suggest using a separate hood or mesh lid with this tank. This 20 gallon aquarium hood review can help you with that.

Additionally, the included filtration system may not be suitable for large fish or species with heavy bioloads as it’s a little on the weak side.


  • Product Dimensions: 27.88” x 16.33” x 20.38”
  • Product Weight: 34.29 lbs
  • Shape: Rectangular


  • Includes a filtration unit, heating device, hood, and light
  • Simple but attractive design
  • Scratch resistant glass
  • Colorful accessories
  • Ideal for tropical fish


  • Hood is a bit flimsy
  • Filter is best used for smaller fish tanks

LANDEN Ultra Clear Glass Low Iron Aquarium Tank

The LANDEN Rimless Clear Glass Aquarium is an aesthetically-pleasing and high-quality fish tank for your aquatic friends, boasting a stunning low-iron construction that makes it ultra transparent.

LANDEN Ultra Clear Glass Low Iron Aquarium Tank

Despite its relatively high price tag, this rectangular shape 20-gallon rimless tank from LANDEN is well worth the extra money due to its striking appearance and superior craftsmanship.

Beautiful Appearance

It boasts a low-iron glass construction, making the tank ultra clear and transparent to enhance your fishkeeping experience. You can do many things with this tank, such as adding a protein skimmer or keeping an extra compartment for experimenting with resins and other media.

Leak Protection

The tank uses high-quality German engineered glue joints to protect it from leaks. It even comes with a thick foam leveling mat to keep the tank stable and secure.

My only worry with this 20-gallon size tank from LANDEN is the possible fragility of it due to its low-iron glass construction. Compared to regular glass, low-iron glass is more delicate and prone to cracking.

Be extra careful when handling this tank, especially when you first set it up!


  • Product Dimensions: 24.4” x 12.2” x 15.74”
  • Product Weight: 42 lbs
  • Shape: Rectangular


  • Made from high clarity low-iron glass
  • Visually stunning
  • Uses high-quality glue joints to prevent leaks
  • Comes with a leveling mat for added protection


  • May be prone to cracking more than regular glass tanks

Aquarium Tank, 20 Gal, Glass

Boasting a strong glass and nonreactive construction, this 20-gallon fish tank is a great selection for saltwater and freshwater fish.

Aquarium Tank, 20 Gal, Glass

Last but not least is the 20-gallon fish tank from SEALUXE, featuring a striking clear glass tank construction that’s welded together with durable silicone rubber.

The sides and the bottom of the glass tank are strong, making it resistant to leaks.

Nonreactive Tank

The glass tank is nonreactive, so it’s suitable for both saltwater and freshwater setups. I really like the black trim along the top and base of the tank as this is a nice decorative touch.

The only downside of this 20-gallon fish tank is that some units can come with too much caulk attached to the bottom rim of the tank.

However, this isn’t very visible and doesn’t affect the quality of the tank.


  • Product Dimensions: 27.8” x 16.3” x 20.7”
  • Product Weight: 30.65 lbs
  • Shape: Rectangular


  • Made from strong glass
  • Durable silicone rubber joints
  • Non Reactive


  • Some units may have a minor visual flaw

How Big Is a 20-Gallon Tank?

A 20-gallon fish tank isn’t huge as it’s still considered a nano aquarium, but it’s still a decent size for many species of fish, including betta fish, dwarf gourami, paradise gourami, ember tetras, neon tetras, zebra danios, guppies, platies, amano shrimp, japanese trap door snails, and a single fancy goldfish.


20-gallon tanks are best used for freshwater fish as many marine fish species require too much space. That being said, some saltwater fish that can be housed in smaller tanks include the clownfish, pajama cardinalfish, yellowtail damsel, royal gramma basslet, and watchman goby.

What Are the Dimensions of a 20-Gallon Tank?

The dimensions of a standard 20-gallon long tank is 30 inches by 12 inches by 12 inches (length, width, height) which provides plenty of horizontal swimming space. The dimensions of a 20-gallon high fish tank is 30 inches by 12 inches by 16 inches.

aquarium on black background
Most of your tank options will be similar in size

What Is the Best 20-Gallon Fish Tank?

The best 20-gallon fish tanks are made from either high-quality glass or acrylic. Glass aquariums are usually cheaper than an acrylic tank, with the bonus of being ultra clear and relatively scratch resistant.

Acrylic 20-gallon fish tanks are less heavy with better impact resistance, making them a good choice for households with small children or pets.

However, acrylic aquariums are prone to scratches and can yellow with age. They can also warp or bow over time, especially when used for marine setups.

Additionally, the best 20-gallon aquariums should feature strong silicone joints to prevent leaks. It should also sit level when placed on a flat surface or aquarium stand.

Is a 20-Gallon Fish Tank Big Enough for Fish?

While some fish prefer a larger tank with more space, others do fine in a smaller one. A 20-gallon fish tank is plenty big enough for fish, though you’ll want to opt for small aquatic life species or nano fish such as neon tetras, platies, guppies, shrimp, and dwarf gourami. If you want to try a smaller tank you can get nano tank like a biocube or nanocube.

Unfortunately, a tank this size is still a little on the small side for some other fish such as African cichlids and common goldfish. But 20-gallon fish tanks tend to have more stable water parameters than smaller fish tanks.

fish tank with a person in the background
There’s enough room for a decent amount of fish (2)

How Many Fish In a 20-Gallon Fish Tank?

How many fish you can house in a 20-gallon fish tank depends on the size and bioload of the species. To help you select the right fish for your new tank, it’s best to follow this rule: 1 inch of fish per 1 to 2 gallons of water.

… 1 inch of fish per 1 to 2 gallons of water.

For instance, fancy goldfish are notoriously messy fish and grow to around 6 to 8 inches in length, so only a single fish can be kept in a tank of this volume.

Other fish like ember tetras can be kept in groups of around 20 to 25 in most aquariums of this size as they produce very little waste and only grow to a maximum of 0.8 inches in length.

The video below has some nice ideas if you’re stumped on what fish to add or aquascaping to do in your 20 gallon tank

Easy Tanks Setups For A 20 Gallon Tank

Fish tanks that are overstocked will require regular water changes and a powerful filtration unit to keep the water clean and healthy.

Your filtration system, digital thermometer, water pump, substrate, decorations, live plants/artificial plants, etc, will also need to be taken into consideration when calculating the number of fish you can house in a tank.

All of these items take up space, reducing the amount of room your fish have to swim.


For example, a 20-gallon tank equipped with a submersible filtration unit, healing device, air pump, water pump, decorations, and all the plants will be unable to house as many fish as a tank of the same volume with external equipment, no decorations, and minimal live plants.

How Much Gravel For A 20-Gallon Aquarium?

Around 1 pound of gravel or substrate per gallon of water is usually sufficient, so a smaller tank like a 20-gallon will require 20 pounds of gravel.

What Watt Heater For A 20-Gallon Aquarium?

aquarium device on white background
A water heater up close (3)

A 100-watt heater is a good choice for a 20-gallon fish tank (5 watts per gallon of water). Heaters with low wattages may not work properly to keep the tank water at a stable temperature.

Final Thoughts

I hope I helped you choose the best 20-gallon fish tank for your needs and budget. Remember to choose one that is both durable and leakproof to keep your fish safe and secure.

If you’re still having a hard time choosing, here are my top choices.

Top Pick

If you’re after a strong 20-gallon tank that comes with a wide selection of extras, the Tetra ColorFusion 20 Gallon Fish Tank Kit is the right pick for you. It comes with everything you need to begin your aquarium keeping journey like a filtration system, light, and hood!

Best Value

Need a good-quality tank but want to save some money? Look no further than the Marina LED Aquarium Kit! It includes basic tank equipment like a light and a filtration system.

Editor’s Choice

Lastly, the Aqueon Starter Kit is one of the best 20-gallon aquariums for beginners as it comes with all the equipment you require to save you time and money!

Feel Free To Share!

Which fish tank did you choose? Be sure to let me know on our social media platforms! And if you need more fish tank equipment recommendations or fish care advice on different species, check out our other articles.

(1) 20130902-IMG_6838 by Kelly Verdeck – licensed under CC BY-ND 2.0
(2) Stella was here by Phil King – licensed under CC BY-NC-ND 2.0
(3) Aquarium heating system on white background by Marco Verch Professional Photographer – CC BY 2.0

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