The Best 20 Gallon Fish Tank: Stocking And Equipment Included

Check out our guide to finding the best 20 gallon fish tank for you, including types of tank, filtration, heating and other equipment!

By Julie Millis
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best 20 gallon fish tank

A 20 gallon aquarium is often the ideal size if you are starting out in fish keeping. The larger capacity means it’s easier to maintain stable water parameters, yet the tank is still compact enough for your home or office.

We’ve gone through weeks of research and validation to bring you this list of the best 20 gallon fish tanks. Overall we chose the Marina LED 20 Gallon Aquarium Kit for its build quality and range of accessories.

But we’ve also covered a range of other 20 gallon fish tanks to cover any scenario, from extra long aquariums to vibrant color tanks – they’re all here!

Do remember though, 20 gallon tanks can weigh 220+ lbs when filled, so we always recommend you use a dedicated 20 gallon tank stand.

That said, let’s go ahead and take a look!

  1. Best Overall: Marina LED 20 Gallon Aquarium Kit
  2. Best For Value: Tetra Aquarium 20 Gallon Fish Tank Kit
  3. Best Starter Kit: Aqueon Aquarium 20 Gallon Starter Kit
  4. Best Long Tank: Aqueon Aquarium 20 Gallon Long
  5. Best Vibrant Color: Tetra ColorFusion 20 Gallon Fish Tank Kit
  6. Best Acrylic: SeaClear Acrylic Aquarium Combo Set
  7. Best For GloFish: GloFish 20 Gallon Aquarium Kit

Best 20 Gallon Fish Tank Picks Reviewed

All the tanks in this list were carefully reviewed and tested against a range of suitability criteria including filtration, lighting, and accessories to arrive at our top picks for any scenario!

1. Marina LED 20 Gallon Aquarium Kit

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 24.0 (l) x 12.5 (d) x 16.5 (h) inches, 35.0 pounds
  • Material: Glass
  • Equipment Included: Slim S20 HOB power filter with cartridges, hood with integrated daylight effect LED lighting, LCD thermometer, 4 inch fish net, Fluval Max fish food, Fluval Aqua Plus water conditioner, Fluval Cycle biological supplement, Aquarium care guide
  • Best for: Overall

Marina’s 20 gallon LED aquarium kit comes with everything you need to start a decent community tank, and is suitable for freshwater or saltwater fish.

The S20 HOB filter has an adjustable flow rate of up to 92 GPH and can cycle your water just under 5 times per hour – more than enough to keep it clean and clear. It also protrudes just 3.8 inches from the back of the tank, so you can get it neatly against the wall.

There’s a convenient feeding door at the front of the hood so no need to lift the whole thing at feeding time, although the hood does hinge all the way for easy maintenance too. And the natural daylight LED lights are powerful enough to support a range of plants.

2. Tetra Aquarium 20 Gallon Fish Tank Kit

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 27.88 (l) x 16.13 (d) x 20.38 (h) inches, 34.1 pounds
  • Material: Glass
  • Equipment Included: Hood with integrated daylight effect LED lighting, Tetra Whisper 20 filter with cartridge, Tetra HT 20 heater, artificial boxwood plant mat, 4 artificial plants, fish net, AquaSafe conditioner sachet, TetraMin food sachet, TetraCare brochure, digital thermometer
  • Best for: Value

Tetra’s 20 gallon fish tank is a really comprehensive kit and offers great value. Not only does it come with everything you need to set up a tank from scratch, it also contains a Tetra HT 20 100 watt heater preset to 78°F – the perfect temperature for many tropical fish. 

The integrated LEDs create a natural light effect which support your fish’s daytime rhythm and will also allow low level plants to thrive. Having said that, Tetra does include 4 artificial plants. They are natural looking and a perfect alternative if you don’t want live plants.

Some owners report the Whisper filter can be a little noisy. But this often occurs if the water level is too low. Ensure the filter is correctly submerged and it is quiet, yet powerful. With its maximum flow rate of 105 GPH it’s enough to keep your 20 gallon tank crystal clear!

3. Aqueon Aquarium 20 Gallon Starter Kit

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 24.25 (l) x 12.5 (d) x 19.5 (h) inches, 33.0 pounds
  • Material: Glass
  • Equipment Included: Low profile hood with cool white LEDs and feeding door, QuietFlow LED Pro power filter with cartridge, preset heater, fish food sample, water conditioner sample, fish net, thermometer, aquarium set up guide
  • Best for: Starter Kit

Aqueon’s 20 gallon aquarium kit contains a well made, sturdy tank along with high-quality equipment. The low profile hood looks sleek and stylish, and the integrated cool white LEDs provide excellent daytime lighting for freshwater setups.

The 3 stage QuietFlow HOB filter can cycle your water up to 5 times per hour with it’s 100 GPH max flow rate. Plenty enough to keep your 20 gallon tank clean. As with all QuietFlow filters the media cartridges are easy to change too.

Add to this the 100 watt 78°F preset heater, thermometer, water conditioner, and food samples, and you have the perfect starter kit for your 20 gallon fish tank setup!

4. Aqueon Aquarium 20 Gallon Long

Photo: Amazon.com

  • Shape and Capacity: Long rectangular, 20 US gallons
  • Dimensions and Weight: 30.25 (l) x 12.5 (d) x 12.75 (h) inches, 22.0 pounds
  • Material: Glass
  • Equipment Included: Rectangular long tank with silicone edges
  • Best for: Long Tank

Whilst the Aqueon 20 Gallon Long Aquarium only consists of the tank itself, it is tough and durable and a great option if you want to be free to choose your own equipment instead of a kit.

Suitable as a freshwater or marine tank, the high-quality glass is silicone sealed at its edges in either a black or clear version. Not only does this look stylish, but it also makes the edges extra durable. Great for withstanding the occasional knock from other pets or kids!

Overall, the extra long narrow shape is an awesome alternative to the standard rectangular shape, both in terms of aesthetics for you and that extra bit of swimming space for your fish!

5. Tetra ColorFusion 20 Gallon Fish Tank Kit

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 27.88 (l) x 16.13 (d) x 20.38 (h) inches, 34.0 pounds
  • Material: Glass
  • Equipment Included: Hood with natural daytime LEDs, Tetra Whisper 20 filter, Tetra HT 20 heater, AquaSafe conditioner sachet, TetraMin food sachet, TetraCare brochure, digital thermometer, 4 inch fish net, 2 Wonderland Plant multipacks, Blooming White Anemone
  • Best for: Vibrant Color

Similar in style and build quality of the previous Tetra tank featured, the ColorFusion has one big twist! The ColorFusion color changing LEDs, which are integrated into the low-profile hood, slowly cycle through a range of vibrant colors making the tank a stand out feature in your room.

You can pause the cycle at any point to fully customize the look of your tank. And the Wonderland Plants and Anemone glow under the light whilst swaying in the current.

With the same Whisper 20 Filter, HT 20 heater, and accessories as the standard Tetra 20 gallon tank, you get all the benefits but in an even more vibrant and colorful tank!

6. SeaClear Acrylic Aquarium Combo Set

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 24.0 (l) x 13.0 (d) x 16.0 (h) inches, 20.0 pounds
  • Material: Acrylic
  • Equipment Included: Hood with fluorescent light fixture (bulb not included), 20-gallon filter, medium gravel substrate, aquarium guide
  • Best for: Acrylic

SeaClear’s Acrylic Aquarium Combo Set comes in a 20 gallon deluxe hexagon version or the standard rectangular version we feature here. Whilst the hexagonal tank is a cool design, the rectangular version is much easier to maintain and stock.

It’s an expensive tank, but if you have children or pets and you are concerned about a glass aquarium it offers a very high-quality alternative. The acrylic used is 17 times stronger than glass so will survive the toughest of home environments!

One downside is it only comes with a fluorescent light fixture and no bulb included, although it would be quite simple to add a separate LED fixture instead. Suitable for freshwater or saltwater use, this tank is a stylish and durable alternative to a standard glass aquarium.

7. GloFish 20 Gallon Aquarium Kit

Photo: Amazon.com

  • Shape and Capacity: Rectangular, 20 US gallons
  • Dimensions and Weight: 24.2 (l) x 12.4 (d) x 16.7 (h) inches, 34.39 pounds
  • Material: Glass
  • Equipment Included: LED hood with GloFish 13 inch LED light stick, Tetra Mini UL heater, Tetra Whisper 20 filter, 3 GloFish plants, GloFish yellow anemone, fish food and water conditioner sample, aquarium set-up guide
  • Best for: GloFish

Another vibrant and colorful option is the GloFish 20 Gallon Aquarium Kit. If you plan to keep GloFish it is the perfect choice as the blue LEDs integrated into the tank’s hood are specifically designed to emphasize the fluorescent colors these fish are bred for.

Also included are 3 GloFish plants and a GloFish yellow anemone, which does a particularly awesome job of reacting to the light and really making the tank stand out.

The 3 stage Tetra Whisper 20 filter has a maximum flow rate of 105 GPH, which will cycle your water 5 times per hour and keep it in great condition. Overall this is an awesome tank suitable for a wide range of species. And it’s great value given the quality and equipment included.

What To Consider When Buying A 20 Gallon Fish Tank

Whether you are new to fish keeping or a seasoned aquarist, a 20 gallon tank is a great choice for any situation. But what are the factors to think about before you buy? Let’s take a look.

20 gallon acrylic fish tank

Why 20 Gallon Fish Tank Kits Are Perfect For Getting Started

If you are new to fish keeping you may be tempted to start small, by looking for a nano aquarium or 10 gallon fish tank. But a 20 gallon aquarium is actually the perfect choice as it’s much easier to maintain stable water parameters for your fish in a 20 gallon tank or larger.

Another benefit of a 20 gallon tank is you’ll have a wider range of fish you can potentially stock, as well as being able to keep a larger community. 20 gallon aquarium kits also tend to come with all the equipment you need, including a heater, which often smaller kits do not.

Your Available Space

If you start out with a regular rectangular tank, you could be looking at one that’s roughly 24 x 12 x 16 inches. Go ahead and measure the base out and you’ll find that whilst it’s a good size it will still fit well in many rooms. But make sure you consider space for a 20 gallon tank stand too.

You also need a little extra room to be able to get round the tank for maintenance. And make sure you choose a location away from direct sunlight or draughts that could interfere with temperature stability of your tank, and from passing traffic like kids or other pets.

Environment

If you are looking for a 20 gallon aquarium, it’s likely you are going to want to start a community of fish. When keeping different species together, you’ll want to ensure they can tolerate similar environmental conditions, particularly temperature and pH.

Many tropical species prefer a temperature between 72 and 80°F, but this does vary so do research compatibility before choosing your fish. Space and habitat also play a part. Gouramis, for example, prefer a well-planted tank with access to the surface to gulp air. 

Should You Add Live Plants?

Whilst live plants are a great addition for any size aquarium, a 20 gallon fish tank starts to become a really good size as you can keep a wider range of species. There’s also more space to add them, and more plants will provide more oxygen and help stabilize the water for your fish.

However, some species can be quite sensitive while they are getting established, and require specific lighting conditions. So if you’re new to the hobby I’d recommend you stick with beginner plants like java fern, cabomba, or anubias which are hardy and easy to grow.

Freshwater vs. Saltwater

Although most beginners tend to start with a freshwater aquarium, a 20 gallon tank is a size at which you may begin to think about saltwater too. But the reason new aquarists start with freshwater tanks is they are easier to keep, need less maintenance, and are less expensive.

I’d only recommend you try a saltwater aquarium in your 20 gallon tank when you have a little more experience. Whilst saltwater fish, corals, and live rock offer a huge range of beautiful species, they are also more expensive, need more maintenance, and there’s less room for error.

Material And Weight

Whilst glass tanks tend to be more readily available, there are also a good range of 20 gallon acrylic tanks nowadays. Which you choose often comes down to personal preference. 

Acrylic tanks can be more prone to scratching, but they can be buffed out easily. If you chip a glass tank, on the other hand, it can be more difficult to repair. Glass tanks tend to offer better clarity for longer as they won’t yellow from the sun or chemicals in the water.

Glass aquariums are heavier. A 24 x 12 x 16 inch glass tank weighs around 33 lbs. Add 20 gallons of water and that’s another 167 lbs [1], before the equipment and decor. Whilst an acrylic tank will be lighter, I would always recommend a proper tank stand for a 20 gallon tank.

Price: Tank Only vs Starter Kit?

When searching for the best 20 gallon fish tank, price can be greatly affected by whether you buy an all-in-one kit or buy your equipment separately. If you are new to fish keeping I’d recommend you start with a kit as they tend to come with all the equipment you need.

They are often high-quality items perfectly suited to the tank, but may offer less customization. Heaters preset to a certain temperature are a good example. So if you do opt for a kit, be aware you may want to upgrade some of your accessories later on down the line.

What Fish Are Best For A 20 Gallon Fish Tank?

There’s plenty of choice when it comes to starting a community in a 20 gallon fish tank. But before you start, make sure you think about how big your fish will be when fully grown. 

For example, depending on the species, Angelfish can grow to between 6 and 12 inches and are not suitable for a 20 gallon tank. Nano fish such as guppies, platies, tetras, danios, mollies, or rasboras are all great options. Or bottom dwellers like corydoras or otocinclus.

Remember not to overstock your tank or it will lead to poor water quality due to too much organic waste. Follow the general rule of 1 inch of fish to every gallon. So in a 20 gallon aquarium, less 1 or 2 gallons for substrate and decor, you could keep 12 to 15 1 ½ inch fish.

catfish in 20 gallon aquarium

What To Look For When Choosing The Best 20 Gallon Fish Tank

So given your needs and the needs of your fish, what should you look for in the best 20 gallon fish tank? There are several factors to consider.

The Right 20 Gallon Fish Tank Stand

Given the potential 220+ lbs total weight of a 20 gallon aquarium, you should use a dedicated 20 gallon aquarium stand to properly support it. As well as the support it provides, you’ll want to choose a stand that fits your room and decor.

Fortunately, there are numerous 20 gallon fish tank stands in wood or metal. And they can range from simple frames to cabinets that provide both functional storage and beautiful design to complement your living space.

Design, Style And Shape

Speaking of design, 20 gallon fish tanks come in a range of shapes and styles that will suit any decor. Some of the most common in the 20 gallon space include rectangular, bow front, and cubes. Fishbowl style spheres are also fairly common in this size nowadays too.

Overall, I believe the best 20 gallon fish tank shape is the standard rectangular prism. It provides plenty of horizontal swimming space, which many fish prefer, and there is room for bottom dwellers and mid-tank schooling fish alike. Rectangular tanks also have a large surface area meaning your water will be better oxygenated than in a tall, narrow aquarium.

Heating And Filtration

20 gallons is a reasonably large amount of water to keep at a consistent temperature. If you are looking to maintain a temperature of around 75 to 80°F, suitable for most tropical fish, you’ll need a heater of 75 to 100 watts.

To keep your tank clean and your water parameters at the right levels, your filter will need to be able to cycle all of the water in your tank around 4 to 6 times per hour. So a filter with a flow rate of 80 to 120 gallons per hour (GPH) is best for a 20 gallon fish tank.

Lights

Standard LEDs or MCR (Multi-Colored Remote) LEDs are the best lights to use for aquariums, and are very common. They provide much more flexibility than simple fluorescent lights in terms of programming, night time and dimmable settings.

For 20 gallon freshwater tanks your LEDs should be around the range of 6500 to 7000k so that they can support your fish and plant life. For saltwater tanks and corals the power output should be higher, at around 11,000k.

Substrate And Decor

Decorating your tank often comes down to personal choice, but do also make sure you take the needs of your fish into account. Many species prefer a well-planted tank with driftwood or rocks where they can hide and mark out territory. Whereas some require more swimming space.

Add around a 1 inch layer of substrate to your tank as a minimum. So for a 20 gallon tank that’s about 20 lbs of substrate. For planted tanks increase to 2 or 3 inches to allow for roots. There are no set rules for the substrate type, but medium size gravel can be easier to clean.

Our Verdict

20 gallon fish tanks are an excellent choice for beginners and seasoned aquarists alike. Their capacity makes them easier to maintain the correct water parameters than smaller tanks, yet they are still a good size for most rooms.

We chose the Marina LED 20 Gallon Aquarium Kit as the best 20 gallon fish tank given the build quality, adjustable filtration, and range of accessories. But if you want a vibrant tank the Tetra ColorFusion 20 Gallon Tank or GloFish 20 Gallon Aquarium are perfect options.

Whichever you go for, it really depends on your individual needs and preferences. But you can be confident that each aquarium featured above are excellent choices for a 20 gallon setup!

FAQs

Here are the answers to some of the most commonly asked questions about choosing the best 20 gallon fish tank.

What Fish Are Best For A 20 Gallon Fish Tank?

Nano fish such as guppies, platies, tetras, danios, mollies, or rasboras are perfect choices for a 20 gallon fish tank. You could also keep shrimp or mystery snails for cleaning!

How Many Fish Should I Keep In A 20 Gallon Fish Tank?

Based on removing 1 or 2 gallons for substrate and decor, you can keep around 12 to 15 1 ½ inch fish in a 20 gallon aquarium if you follow the 1 inch of fish per gallon rule.

How Often Should I Maintain A 20 Gallon Fish Tank?

20 gallon tanks tend to have more stable water parameters than smaller aquariums due to their larger water volume. Check your parameters at least weekly and if they are stable you may be able to do a fortnightly 10 to 15% water change. Do clean the tank glass weekly though.

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AUTHOR
Julie Millis
Julie has worked in aquatics for over 15 years. She is passionate about freshwater and saltwater tanks. Julie loves helping with all your fish-keeping questions!

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