When people ask me what tank size they should begin with I always suggest the 20 gallon fish tank. The size is big enough for you to keep more than a handful of fish. while still being small enough to be easily cleaned and inexpensive.
But which 20 gallon tank is right for you?
The best 20 gallon aquarium is the one that matches your aesthetic preferences. They come in acrylic constructions, crystal clear starfire rimless models, glofish tanks with neon gravel, and more!
Once you have the aquarium, you’ve only just begin! You’ll still need to get filters, substrates, lights, and many other items. Fortunately, I’m here to walk you through all of that!
Are you already thinking of fish stocking ideas? If so, then feel free to whet your appetite with this video on stocking 20 gallon aquariums:
Best 20 Gallon Fish Tank – Top 5 Choices
Whether you want just the tank itself or an entire kit, there are a number of great options to explore! These are by far the best 20-gallon fish tanks to choose from:
Oceanic Systems 20 Gallon Long
| Dimensions | 30.25 x 12.5 x 12.75 inches |
| Weight | 22 lbs |
| Star Rating | 4.3 Out Of 5 |
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Many of the 20-gallon fish tank models you see for sale are of the high variety. But the 20-gallon long is a classic for many good reasons. Long-style aquariums are often called “breeder tanks” because they offer more room along the bottom than “high aquariums.”
This model by Oceanic Systems is ideal for fast-moving fish that need extra swimming room. Danios, tetras, and rasboras all do better in 20-gallon-long tanks.
The design is otherwise identical to a classic 20. The joints are sealed using silicone and black rims hold the tank together.
Standard glass with iron is used, which is scratch resistant and durable. Unlike an acrylic tank glass doesn’t scratch easily. So you won’t need specialized cleaning tools to remove algae or biofilm from the inner surfaces. Nor does it discolor over time due to exposure to lights.
The floor dimensions of 30.5 x 12.5 inches are also standard size. Ensuring that finding an aquarium stand will be a simple matter.
Pros
- Scratch-resistant glass that retains clarity for the lifetime of the tank
- The longer design offers more space for fish to swim in a straight line
- Long-style tanks offer more bottom area for live plants to prosper
- Standard dimensions for an aquarium tank stand
Cons
- Not as much light transmittance as starfire glass
- Tank by itself, rather than a kit with filter, lights, and other suitable accessories
Tetra ColorFusion Aquarium 20 Gallon Fish Tank Kit
| Dimensions | 24.2 L x 12.4 W x 16.7 inches |
| Weight | 34.4 lbs |
| Star Rating | 4.4 Out Of 5 |
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When buying a 20-gallon fish tank sometimes you want a kit that contains everything. These make excellent aquarium gifts for beginners who might feel overwhelmed if you were to just gift them an empty tank.
Like the Glofish Aquarium Kit, the Tetra ColorFusion also includes an LED light. I recommend LED light setups for most aquarium kit purchases because they use less power than fluorescent fixtures. LEDs also run longer and the lighting output (wavelength, color temperature, etc) is more customizable.
Lighting is a central element to the Tetra ColorFusion because you can set the output to cycle through several different colors. Or you can choose one color, depending on your mood that day.
This 20-gallon tank kit also comes with more equipment to have you up and running faster. A Tetra Whisper 20-gallon tank filter, which is an excellent power filtration system.
The heater is of the right size for the unit. Along with a net, fish food, a thermometer, and conditioner to make tap water safe! The only thing left to get is decorations and fish!
Pros
- Everything except decor and fish included
- LED lights can cycle through multiple colors
- Excellent Tetra Whisper power filter
- Fish food, water conditioner, and other suitable accessories
Cons
- Only a small amount of food and water conditioner
SeaClear Acrylic Aquarium Combo Set
| Dimensions | 24 x 13 x 16 inches |
| Weight | 20 lbs |
| Star Rating | 4.2 Out Of 5 |
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The minimalist style and crystal clarity of a rimless low-iron aquarium are hard to resist. But perhaps the price and weight aren’t right for you. In that case, take a look at the SeaClear Acrylic Aquarium Combo Set.
Being a single piece of molded acrylic the tank has a rimless style. Corners mesh well and there is no black plastic trim to distract from the floating cube effect. Acrylic tanks are both impact resistant and lightweight. Making it more reliable than glass when young children are around.
You also have the option of a 20-gallon hexagonal aquarium, if you want something even more intriguing as an interior decor option!
A 15-inch lighting unit is also included, with reflectors to direct light for ideal fish viewing. The bulbs are contained in a rectangular black housing, furthering the effect generated by the clean lines of the tank.
No filter or decor comes with the kit so consider the options I’ve included below!
Pros
- Impact-resistant, high-clarity acrylic walls
- Lightweight and easy to move
- Includes light
- Comes in several sizes, including a 20-gallon hexagon
Cons
- Acrylic is less durable than scratch-resistant glass
- Starter kit does not include filter or decorations
Aqueon Aquarium Starter Kit with LED Lighting
| Dimensions | 24.25 x 12.5 x 19.5 inches |
| Weight | 33.05 lbs |
| Star Rating | 4.5 Out Of 5 |
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The Aqueon Aquarium Starter Kit with LED Lighting is the best aquarium kit if you don’t want to flash colorful lights or admire an unusually shaped tank.
The setup includes a standard 20-gallon high tank (24.25 x 12.5 x 19.5 inches) so you can be sure it will be easy to find a matching stand. The hood uses cool white LED bulbs with a bright output. Providing a neutral yet pleasant fish viewing experience versus multiple colors.
A liquid crystal stick-on thermometer and preset heater ensures the water remains warm for tropical fish. You also get a net and samples of water conditioner and fish food!
The included filters are designed by Aqueon, which I’m a fan of. Their power filters give added space for beneficial bacteria to colonize. It’s similar to the bio wheel concept by MarineLand except with fewer moving parts.
Pros
- Filter, heater, and lights are included
- Standard sized 20 gallon glass aquarium
- Cool white LED bulbs with a beautiful output
- Fish food, water dechlorinator, and net included
Cons
- Lights are neutral in color, which some people might not prefer
- No decor options like gravel or rocks
GloFish 20 Gallon Aquarium Kit with LED Lights, Decor, Heater, And Filter
| Dimensions | 24.2 x 12.4 x 16.7 inches |
| Weight | 35 lbs |
| Star Rating | 4.4 Out Of 5 |
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Glofish are genetically engineered tetras, barbs, and danios that glow a bright pink, green, purple, or orange under the right conditions. They do well in normal aquariums but you can really show off their radiance with a tank kit designed for them.
This starter kit includes everything you need for glofish. The most important thing is the LED light that is included. Glofish fluoresce under ultraviolet lights, which aren’t a part of the usual aquarium kit. The included Whisper 20 filter is sized for a 20-gallon fish tank.
You also get a heater, since these are tropical fish. The decor is also just as fluorescent as the fish. The colorful pebbles, anemones, and plants all shine a bright neon when the blacklights are turned on.
Small samples of food and water conditioner are included. But you’ll need to stock up soon enough. In an aquarium tank this size, you could keep up to 10 glofish, depending on the species!
Pros
- Decor and lighting perfectly matched to glofish
- Includes filter, heater, lights, food, and water conditioner to get tank running in just minutes
Cons
- Design is less customizable and may not meet your aesthetic preferences
- Does not come with much food or water conditioner
How To Choose The Best 20-Gallon Fish Tank – Things To Consider Before Buying
There is a 20-gallon tank for almost any application. But how do we know which design is suitable for our needs? Here are some questions to help you narrow down the options presented here!
What Kind Of Fish Do I Want?
One of the most important decisions is knowing what kind of fish will be living in your 20-gallon fish tank. What if you know you want to set up a tetra tank or another system for active species?
Then a hexagonal or high design fish aquarium isn’t the right tank. You’ll want a long-style tank, which provides more horizontal swimming room!
If you want to try keeping glofish then an aquarium kit with ultraviolet black lights is important. That way you’ll be able to appreciate their fluorescence without an additional purchase!
The fish you have in mind also affects the sort of filter and decorations you need to buy. A crowded tank means you’ll need a capable power filter. Or maybe even a canister filter. For a minimalist setup you might consider a sponge filter instead.
You don’t have to have the entire community tank planned out in advance. But a basic vision does help, in the long term!
Do You Want Live Plants?
I’m a big fan of keeping live plants alongside aquatic creatures. They offer a tremendous range of benefits. Plants consume carbon dioxide, releasing oxygen in exchange for fish to breathe.
They also use ammonia and other byproducts of the nitrogen cycle. Turning fish waste into fertilizer that spurs lush green growth. And don’t forget just how beautiful plants look!
But the one thing that all plants need is full-spectrum aquarium lights. Not all fish tank kits come with one. So take a moment to read a product listing carefully. Hoods with incandescent lights will have too warm of a color spectrum to grow plants effectively.
Fluorescent and LED light is most suitable for plants. But you still need photosynthetically active radiation (PAR); not just any light will do.
Since planted tanks are very popular these days, many light manufacturers now include a PAR spectrum with their lights. So you can be sure that a given lighting setup will be good for live plants!
And if all of this sounds too high maintenance to you? Then consider buying artificial plants instead! Silk and plastic plants can look very convincing.
They require no fancy lights, fertilizers, or trimming. And they are easy to scrub free of algae or biofilm as needed, keeping them lush and green for years to come!
Glass Versus Acrylic?
When people shop for aquariums they usually gravitate towards glass. Which is a shame when there is a very good alternative available: acrylic! Acrylic tanks are made of molded plastic.
They are less popular nowadays than they used to be but are still easy to find in smaller aquarium sizes (3 to 20 gallons).
An acrylic tank kit offers several tradeoffs versus a glass aquarium tank. For one, they are 50-60% lighter than glass. Perfect for medium to large-sized setups like 20-gallon aquariums. And if you get into larger aquariums the weight savings can be several hundred pounds compared to a tempered glass aquarium.
Acrylic holds in heat better than glass, lowering the amount of power consumed by your heater.
It is also very impact-resistant; up to 17 times stronger than glass at weathering a sudden impact. So if you have kids that enjoy testing the structural limits of household items, it will be safe.
Lastly, acrylic is easier to mold than glass. So fish keepers that want hexagons, wavy bowfront panels, and other shapes will have an easier time finding inexpensive acrylic tanks in these shapes.
The flip side is that acrylic is much easier to damage compared to scratch-resistant glass. Even using the wrong cleaning brush can leave permanent scratches. You need a brush designed for acrylic aquariums.
Otherwise, the acrylic panels will grow cloudy from micro scratches. Algae can also grow inside of them, forming green streaks across your viewing area.
Acrylic tanks sometimes cloud over several years due to visible and ultraviolet light exposure. The plastic degrades from the constant presence of intense light. This is normally only an issue for only the cheapest acrylic tanks in very small sizes, however.
Best 20 Gallon Fish Tank Stands
Since the 20 gallon aquarium is a standard size, it is easy to find stand that fits one. That said, there are three that are better than normal thanks to their build quality and aesthetic qualities!
Ameriwood Aquarium Stand
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Wooden stands are a classic in the aquarium hobby. They are solid, look great in any living space, and usually come with doors. Doors are important because you can close them, hiding fish tank supplies from view. This wooden stand by Ameriwood even has shelf space for added decorations, if you wish!
LANDEN Aquarium Wooden Stand and Cabinet Tank
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The clean, minimalist presentation of this wooden stand by LANDEN is a perfect match to the neon colors of a marine setup. Since the top is sized precisely to match a 20 gallon aquarium it creates the effect of a pillar. The layout fits into the interior design scheme of any home or office space.
Caitec Double Aquarium Stand
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Metal aquarium stands offer some benefits over wood. They don’t decay with repeated water exposure. And while they don’t hide equipment underneath, the extra space in this stand serves a dual purpose. Caitec stands enable you to keep two aquariums stacked on top of each other! This brand only makes 20 gallon long stands, however. So choose accordingly.
What Items Does A 20 Gallon Fish Tank Need?
Once you have your tank and stand, it’s time to start adding some accessories!
Best Filter For A 20 Gallon Fish Tank
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The filter of your fish tank is its life support system. Without one, your aquatic pets would eventually suffocate on their own waste.
If you’re looking for a hang-on-the-back power filter, the Marineland Penguin Bio-Wheel Power Filter is one of the best. They were the first to create the Bio-Wheel design, which vastly improves the amount of surface area available for beneficial bacteria to colonize.
Space in the rear of the unit holds a proprietary-sized filter cartridge that uses cotton floss and activated carbon. Coupled with the bio wheel you have a complete mechanical, chemical, and biological filtration system.
Best Heater For A 20 Gallon Fish Tank
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No 20-gallon fish tank is complete without a heater. Not if you want to keep tropical fish healthy and active.
As a rough rule of thumb, you want heaters that output 3 to 5 watts per gallon of power. Any less and the heater won’t be able to keep up with fluctuations in water temperature.
My favorite is the FREESEA 100 Watt Aquarium Fish Tank Heater. It is fully submersible so you can hide it behind decorations. Unlike clip-on heaters, which take up visual real estate. It also comes with a digital thermometer, giving you an accurate read out of water temperature down to .1 degrees Fahrenheit!
Best Lighting For A 20 Gallon Fish Tank
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Lighting is very important for a fish tank. It not only helps you see what’s inside but it also nourishes any live plants that you add. Plants need photosynthetically active radiation (PAR) to grow well.
The NICREW ClassicLED Plus Planted Aquarium Light provides just this using led light output. LEDs run cooler than fluorescent or incandescent lights. And they are more energy efficient while still providing the right spectrum for plants and viewing.
Nicrew’s 24-30 inch model is just the right size for both a 20-gallon high (24 inches) or long-style (30 inches) aquarium kit.
Best Substrates For A 20 Gallon Fish Tank
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The best aquarium sand and gravel depends on what you find to be beautiful. As for me, I enjoy natural-looking substrate options over unrealistic painted-on colors.
Gold Pearl by AquaNatural is my favorite general-use substrate for a 20-gallon tank kit. The grains are small enough to avoid harming burrowers like cory catfish or kuhli loaches. Yet it’s not so hard to clean or aquascape with as sand.
One pound per gallon of tank size will give you enough substrate to coat the bottom. So you’ll want two bags of Gold Pearl!
If you’re planning on adding loads of live plants then a soil-based planting substrate is a good idea! Fluval Stratum substrate comes in 4.4 lb. bags of baked soil.
Aquatic plant species root better and grow much faster in soil-bottomed tanks. It also moderates the water chemistry, bringing the pH closer to neutral, which plants and many fish prefer!
Best Lid For A 20 Gallon Fish Tank
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The black matte color of the Aqueon Aquarium Black 20″ Fluorescent Deluxe Full Hood is a classic. A front door allows you to easily feed your fish and perform water changes without removing the entire lid. The unit holds space for a 20-inch fluorescent light bulb, which comes included so you can have the tank lit up in just minutes!
Best Decorations For A 20 Gallon Fish Tank
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Besides gravel, aquarium plants are the next decoration you should consider. Since live plants can be a lot of work, I recommend plastic plants to get your started. They provide cover for fish and won’t wilt or need fertilizing. This variety pack by PietyPet includes plastic plants of various sizes, designs, and colors!
Best Accessories For A 20 Gallon Fish Tank
Last but not least, we need accessories for performing general maintenance. These tools are indispensable for aquarium owners:
20-Gallon Fish Tank Dimensions & Size – How Big Is A 20-Gallon Tank?
The exact dimensions of a 20 gallon tank depends on the design of it. Some of the models I’ve included above are specially designed to be different.
But there are two standard sizes that you’ll find almost anywhere:
- 20-Gallon High Aquarium: 24 x 12 x 16
- 20-Gallon Long Aquarium: 30 x 12 x 12 inches
Make sure your stand and lights are sized for the right variety. Filters, heaters, and other equipment work as well on one as the other, though!
How Much Does A 20 Gallon Fish Tank Weigh?
A full 20-gallon tank weighs more than you might think. An empty glass tank of this volume will weigh around 25 lbs. Not too bad, right?
Well, water is very dense. So once it’s full of water, decorations, and technological accessories, it’s beyond the ability of most people to life. A full 20 gallon tank will weigh roughly 225 lbs.
This means that most tables aren’t good alternative stands. If you don’t trust one to hold your own weight or more then make sure you buy an aquarium stand.
How Many Fish Can Fit In A 20 Gallon Tank?
I find that the 20-gallon fish tank is the best option for beginner aquarists. It’s a small enough space to be easily managed and inexpensive. Yet it offers twice the volume of the popular 10-gallon fish tank.
A 20-gallon glass aquarium allows you to keep more fish. As well as larger species that would not fit in a smaller tank. Dwarf cichlids and smaller gouramis are deep-bodied and colorful fish that would be cramped in a 10-gallon fish tank.
These fish also have remarkable personalities. They display parental care and other behavior that makes them a step up beyond smaller community fish! That said, smaller fish are just as fine an option for a 20-gallon aquarium.
What if you find you can’t decide between a group of neon tetras and a group of cherry barbs?.. Well, why not keep both? That would be too many fish for a 10-gallon fish tank but a 20 can house both species with comfort!
As a general rule of thumb, you can keep one inch of fish per gallon of water. Fish that reach a maximum adult size of 3 to 4 inches will also live comfortably in a 20-gallon fish tank.
Best Freshwater Fish For A 20 Gallon Tank
Freshwater fish tank keepers have an endless selection of fish to choose from. Here are some of my favorites for this tank size!
Nano Aquarium Fish (Less Than 1 Inch)
Nano fish are, in my view, very underappreciated. These fish are often hard to find in big retail pet stores. Too few aquarists know what they are and are underwhelmed by their adult sizes. Specialty aquarium shops will carry them, however.
Nano fish don’t grow larger than 1 inch long. Many are boldly colored. And their diminutive size means you can keep huge schools of them, even in a 20 gallon fish tank. Add some live plants and invertebrates and you’ll have a display worthy of a public aquarium!
- Pea Puffers: pea puffer fish are round freshwater puffers that look like floating jellybeans with eyes. They are adorable and hardy but very aggressive. Best kept in a species-only tank.
- Chili Rasboras: small schooling rasboras with intense red colors. They contrast well with plants and live peacefully with invertebrates and other fish.
- Endler’s Livebearers: the smaller cousins of guppies. Just as easy to care for and the males have beautiful neon colors.
- Red Cherry Shrimp: small freshwater shrimp. They swim freely in the water column and feed on fish flakes and algae. Red cherry shrimp are hardy and very prolific breeders.
- Taiwan Bee Shrimp: these invertebrates are more sensitive to poor water quality than red cherry shrimp but not difficult to care for. Taiwan bee shrimp are even more beautiful and the babies are easy to sell back to local fish stores.
Small Sized Fish (1 To 2 Inches)
Small freshwater aquarium fish are the most common choices offered by local pet stores. The 1 to 2-inch scale is ideal for 10 and 20-gallon aquariums. All of them are hardy and get along well together. Truly your choices are endless in this size category. But here are a few popular selections I recommend:
- Platies and other Livebearers: livebearers are probably the easiest aquarium fish to breed. They thrive in the same hard, alkaline water that comes out of the tap. And they eat everything from brine shrimp to algae!
- Zebra Danios: all danios (except giant danios) are a good fit for 20 gallon tanks but zebra danios are exceptionally hardy. They were the first egg laying fish I was able to spawn. And they can even live in unheated fish tanks alongside other cold water fish.
- Tetras: tetra fish are small but very active. They live in schools as well so you’ll need at least six of them, if not more. Tetras are a little demanding when it comes to water quality. And they aren’t easy to breed. But they are otherwise great fish to keep!
- Corydoras: cory catfish come in dozens of different species. Unlike many other fish that live along the bottom, cories are active day dwellers. They are also social so you’ll want at least 3!
Medium Sized Fish (3 To 4 Inches)
One of the best things about a 20 gallon fish tank is that you can start exploring medium sized aquarium fish. Nothing too large; 3 to 4 inches is going to be your maximum size. And you don’t want highly active fish that are this size.
But 20 gallons is where you can start thinking about dwarf cichlids, smaller gouramis, and loaches. Just be careful when keeping cichlid pairs. If they spawn, even a 20 gallon tank will be too small. They are vicious parents and may bully or even kill their tank mates.
- Dwarf Cichlids: this category includes a number of common aquatic creatures, including German blue rams (Mikrogeophagus ramirezi), Kribensis (Pelvicachromis pulcher), and convict cichlids (Amatitlania nigrofasciata). Cichlids are more sociable than most fish and colorful, to boot!
- Dwarf Gourami: most gouramis are too large for a 20 gallon tank but the dwarf gourami is an exception. These fish are peaceful and come in a wide range of color morphs. Gouramis build bubble nests and care for their fry.
- Betta Fish: bettas are close relatives of gouramis. While they can be kept in tanks as small as 5 gallons they do enjoy having extra space. Many aquarists think that bettas have to be kept alone but this is false. Betta fish males are only intolerant towards each other. Sometimes they will chase other fish but rarely to kill.
- Kuhli Loaches: few fish are a better match for the bottom of the tank than kuhli loaches! These worm-like scavengers are highly active and love to burrow. So provide a sand substrate, if possible, so they don’t scratch themselves trying to burrow into gravel
Freshwater Stocking Suggestions
Here are some stocking suggestions to get your tank populated with colorful fish! Don’t forget to cycle the aquarium beforehand by growing a healthy colony of beneficial bacteria!
- 6x Endler’s Livebearers, 10x Chili Rasboras, 6x Red Cherry Shrimp
- 1x German Blue Ram, 2x Kuhli Loaches, 2x Platies, 6x Tetras
- 1x Betta Fish, 6x Zebra Danios, 4x Corydoras
Best Saltwater Fish For A 20 Gallon Tank
20 gallon tanks are considered nano tanks in the world of saltwater setups. The fish are more sensitive to dissolved nitrogenous waste. So we need to be extra-careful to not over stock the tank. But you do have some options here!
Saltwater Fish For A 20 Gallon Tank
Here are some of my favorite saltwater fish for this size setup:
- Clownfish: everyone loves clownfish for good reasons! They are colorful, have an adorable swimming pattern, and have an amazing symbiotic relationship with sea anemones. Only the smaller species can live in a 20 gallon, however. Two of the best are pink skink clownfish (Amphiprion perideraion) and percula clownfish (Amphiprion percula).
- Damselfish: clownfish are members of the greater damselfish family. Damselfish are schooling fish and some grow to be large and mean. Yellowtail blue damselfish (Chrysiptera parasema) and the other members of the Chrysiptera genus are small, peaceful additions to a small saltwater community tank!
- Fire Gobies: also called firefish (Nemateleotris magnifica). Provide them with plenty of possible hiding places. That way they feel safe enough to spend more time out in the open!
- Cleaner Shrimp: these gorgeous shrimp are mostly in the genus Lysmata. They are peaceful and will clean loose skin and parasites from the sides of fish. Cleaner shrimp also eat leftover flakes and other crumbs so they don’t decay.
- Royal Gramma: also known as the fairy basslet. Grammas are territorial but as long as you give them a cave to defend they won’t bother their tank mates. Grammas are hardy and easy to feed.
- Neon Goby: small, social, and even offer cleaning services to their tank mates. What better bottom dweller could you ask for than the neon goby?
- Dottybacks: the dottyback group is a controversial choice. They are beautiful, small, and some of the hardest to kill marine fish. Their one flaw is that they are quite aggressive towards other fish. So you’ll need either a single dottyback – or a mated pair – in a 20 gallon tank. You can keep them with invertebrates like shrimp and sea anemones, though!
Saltwater Stocking Suggestions
Once your tank is well cycled, you might want to consider the following fish combinations!
- 2x Clownfish, 1x Cleaner Shrimp, 1x Sea Anemone, 1x Royal Gramma, 6x Neon Goby
- 6x Yellowtail Blue Damselfish, 1x Royal Gramma, 1x Clownfish, 1x Cleaner Shrimp
- 1-2x Orchid Dottyback, 1x Cleaner Shrimp. Keep your dottyback pair with invertebrates like corals, snails, hermit crabs, feather duster worms, and starfish!
Conclusion – Best 20 Gallon Fish Tank
20 gallon tanks are a good step up from the usual 10-gallon setup. They offer more space for fish without being too time-consuming to manage. Giving you twice as many choices for your next freshwater or marine setup!
