20 Gallon Fish Tank Stocking Ideas

When it comes to setting up a new 20-gallon fish tank, you might be looking for ideas on which fish to keep. These low-maintenance, budget-friendly tropical fish make perfect, peaceful housemates. Curious about the ideal setup for a 20-gallon tank? Let’s explore which fish can live comfortably in a 20-gallon environment.

by Fabian

Updated: September 13, 2023 / 8 mins read

Fabian is the dedicated Chief Editor at Aquarium Nexus. From a young age, he was captivated by the vibrant world of aquatic life, leading him to accumulate over 20 years of experience in keeping and breeding various fish species. The fulfillment derived from the aquarium hobby has remained a constant throughout Fabian's life. As an expert in the field, he finds great pleasure in imparting his extensive knowledge and personal experiences to both seasoned aficionados and budding enthusiasts.

Best Freshwater Fish for a 20 Gallon Fish Tank

Fish enthusiasts have a myriad of options when it comes to the types of fish they can stock in a 20-gallon tank.

Livebearers

Livebearers are freshwater fish that give birth to free-swimming young ones by retaining their eggs inside the body instead of hatching them.

These types of fishes are arguably the most common in aquariums, with most of them coming from the Poeciliidae family. They include mollies, guppies, mosquito fish, platies, and swordtails.

One advantage of keeping these fish species is that they are quite easy to raise because newborns are usually larger than the young ones of egg-laying species. This is why many fish breeding enthusiasts recommend them for beginners.

It’s important to note that some male species in the Poeciliidae family fight each other when competing to mate with females. As such, it’s best to keep these fishes in groups of three: two females and one male.

Mind you, livebearer females can birth young ones throughout their lifetime. Therefore, plan for the fry adequately if you choose to keep livebearers.

Tetras

Out of all the different kinds of tetras out there, neon tetras are the most popular when it comes to aquarium fish keeping.

Nonetheless, most tetras have small, compressed, and brightly-colored bodies. And they are extremely easy to rear, although it’s best to keep them in schools of five to six fish.

Additionally, tetras go a long way in making aquariums attractive. Other than Neon tetra, Black Neon Tetra (1.6 inches), Glowlight Tetra (1.6 to 2 inches), Diamond Tetra (2 inches), Rummy Nose Tetra, Ember Tetra, and Black Phantom Tetra (1.8 inches) can do exceptionally well in a 20-gallon tank.

Rasboras

Rasboras are arguably the best type of fish for small community tanks, thanks to their active lifestyle and vibrant colors.

These fish originate from the freshwater habitats of southeast China as well as Southeast and South Asia. Some examples of Rasbora species regularly kept in aquariums include Scissortail (5 inches), Red-lined (2.5 inches) Pygmy (0.5 inches), and Harlequin Rasboras (2 inches).

Because of their peaceful nature, Rasboras are excellent tank mates. Also, these fish show unique shoaling behaviors on top of having impressive colors.

Danios

The most popular from this family are the Zebra Danios, which are extremely active fish that usually stay in the upper levels of an aquarium.

They are native to Southern Asia and require a large tank because they love to swim when chasing each other or when finding food. Also, the zebra danios are most happy in schools of five to six fish.

What’s more, these fishes can fight with other long-finned fish like guppies and angelfish. So consider this when stocking up your aquarium. Other Danios you can keep in a 20-gallon tank include Fire Ring Danios, Pearl Danios, and Celestial Pearl Danios.

Cory Catfish

Cory catfish are mainly bottom feeders, making great helpers when cleaning the tank.

Since they are timid, it’s advisable to keep them in shoals of 5-6 or more. These freshwater catfish aren’t aggressive at all, though they prefer soft, acidic water.

Some of the most popular Corydoras species that you can house in 20-gallon aquariums are: panda corydoras, bronze corydoras, pigmy corydoras or corydoras Similis.

Barbs

Barbs are hardy, lively, and colorful fish. They are very fun to watch because they are in constant motion across the aquarium.

Barbs prefer living in schools of at least five or six. Most barbs (especially tiger barbs) are aggressive fish and don’t get along with long-finned or slow-moving fish. Barbs are fin nippers and can harm and kill other fish species.

Some of the most peaceful barbs are rosy barbs, cherry barbs, golden barbs, or Odessa barbs.

Gouramis

In addition to being easy to keep, Guaramis are pretty hardy fish. They are peaceful, slow-moving, but active fish, ideal for a community tank.

Currently, there are over 130 recognized species of Guaramis, with most of them showing parental care to their young ones. Some of the most common gouramis that can be kept in a 20-gallon aquarium are honey gourami, dwarf gourami, sparkling gourami, or pearl gourami.

Cichlids

When we refer to cichlids, most aquarists think of African cichlids, which can’t be kept in a 20 gallon fish tank.

In fact, there are many types of cichlids out there such as angelfish, dwarf cichlids, or ram cichlids, that you can put in 20 gallon tanks.

Discus fish, and Oscars can get pretty big, and quickly outgrow a 20-gallon fish tank, so they will require a larger tank.

Cichlids are really cool fish. They can become territorial, especially in the breeding period. Cichlids will pair up and will raise the fry together, male and female.

Shrimp

Aquarium shrimp can add a fun element to your tank because they come in a range of sizes and colors. This has made their popularity increase tremendously over the last couple of years. What’s more, there are shrimp species that act as cleaners.

The best part about keeping shrimps is the feeding routine. Shrimp are scavengers that will eat just about anything including both animals and plants (dead or alive).

Furthermore, female shrimps are unique in that they carry eggs on their bodies’ underside. These invertebrates also molt as they grow, which makes them shed exoskeletons from time to time.

Betta Fish

Betta fish also known as the Siamese Fighting Fish are one of the best fish that are kept alone. Though, they are a great addition to any community tank. It can thrive in a 20-gallon aquarium if the tank mates are chosen correctly.

Bettas are slow-moving fish but are scavengers. They will swim around the whole tank but mostly stay at the water surface. Choosing a betta fish for a community tank requires some attention. Try to choose a female betta, because males are more aggressive. For tank mates, choose peaceful, but fast-moving fish.

Shrimp can also live with betta fish, though you will need to provide them with cover because bettas like to snack on small shrimplets.

20 Gallon Stocking Ideas with Pairing Examples

Evidently, there are many fish species you can keep in your aquarium, but not all of them will survive or thrive in a 20-gallon tank.

Additionally, not all species can coexist harmoniously. Therefore, it’s crucial to know which species can be housed together and which ones should be kept apart. Below are several examples of freshwater fish combinations you can consider for your 20-gallon setup:

Idea #1: The Colorful Community

• The Eye Catcher: 3 Guppies, 2 Mollies, and 2 Platies.
• The Swarm: 6 Neon Tetras, 3 Black Phantom tetras, and 5 Glowing Tetras.
• Ground-level: 6 Dwarf Corydoras such as the Panda Corydoras Catfish, Skunk Corydoras Catfish, or Albino Corydoras Catfish.

Idea #2: The Blue Heaven

• The Eye Catcher: 1 pair (male and female) of German Blue Ram, Electric Blue Ram or, the Angel Ram
• The Swarm: 8-12 Neon Tetras
• Ground-level: 6-8 Cory Catfish

Idea #3: The Yellow Bliss

• The Eye Catcher: 1 pair of the yellow Dwarf Cichlid
• The Swarm: 8-10 Neon Tetras
• Ground-level: 6-8 dwarf Cory Catfish

Idea #4: Endler’s Paradise

• The Eye Catcher: 3 females and 2 males from the Endler Guppies species.
• The Swarm: 8-10 Neon Tetras
• Ground-level: 6-8 Dwarf Cory Catfish

Idea #5: The Sweet Harmony

• The Eye Catcher: 1 pair (male and female) of Honey Guarami
• The Swarm: 8-12 Rasboras fish such as Lambchop Rasbora, Harlequin Rasbora, Glowlight Rasbora, Dwarf Rasbora, or Red Dwarf Rasbora.
• Ground-level: 8-12 cherry shrimp (make sure you provide a lot of cover for the shrimp in order to protect them from the fish)

Idea #6: The Celestial Zone

• The Eye Catcher: 10 Celestial Pearl Danios
• Additional Stocking: 6-8 Corydoras

Idea #7: Guppy Glow-Up

• The Eye Catcher: 4 female and 2 male Guppies
• The Swarm: 8-12 Rasboras or Tetras
• Ground-level: 6-8 Cory Catfish

Idea #8: Puffer’s Playground

• The Eye Catcher: 1 pair of Dwarf Pufferfish
• The Swarm: 8-12 Rasboras
• Additional stocking: 10-15 ramshorn snails or cherry shrimp

Idea #9: The Platies Party

• The Eye Catcher: 4 female and 2 male Platies
• The Swarm: 8-12 Rasboras or Tetras
• Ground-level: 6-8 Dwarf Cory Catfish

Idea #10: Betta Bliss

• The Eye Catcher: 1 pair (male and female) of the Crescent Betta or Peaceful Betta
• The Swarm: 8-12 Rasboras
• Ground-level: 10-15 shrimp (with lots of live plants and hiding places)

Final Thoughts

Take note that you should stock your aquarium considering the general rule of thumb of one 1-inch fish per gallon of water. This means that a 20-gallon tank can hold in total of 20 inches of fish. Always take into account the adult size of the fish species before stocking up.

Also, ensure that your aquarium environment fits the species of fish you want to bring in. Research the requirements of each fish species you want to keep and make sure you can provide them with an optimal environment.

I really hope that this quick guide has helped you choose the best fish for your 20-gallon aquarium. If you have any questions or suggestions, feel free to leave a comment below.