20 Gallon Aquarium Stocking Ideas

Did you that there are over 139.3 million freshwater fish kept as pets?

If anything, freshwater fish are the largest number of pets kept in the US, considering that there are 89.7 million dogs and 94.2 million cats.


20 Gallon Aquarium Stocking Ideas

So why do many people choose to keep fish in aquariums? Firstly, they provide health benefits like reducing stress, heart rate, and blood pressure.

There are even studies showing that aquariums can help improve eating habits and behaviours of people suffering from Alzheimer.

What’s more, fish pets are ever-quiet, making them a perfect fit for families with young parents. They are also way cheaper than other pets and don’t require a lot of maintenance.

If you don’t have an aquarium just yet, I highly recommend buying an aquarium kit. The Tetra 20 is a complete aquarium kit, which you can purchase from Amazon.

This fish tank kit includes all you need to get started, such as LED hood, filter, heater and artificial plants.

So if you’re looking to install a 20-gallon aquarium, you’re definitely making the right decision. Even so, you’ll need worthwhile ideas on how you can stock it perfectly. Check out the guide below:

Best Freshwater Fish for a 20 Gallon Aquariums

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

Some examples include:



Guppy Fish (source)

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

This 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 livebearers 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 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.



Neon Tetras (wikipediaCC BY-SA 4.0)

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

Nonetheless, most tetras have small, compressed, and brightly-coloured 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 making in aquariums attractive. Other than Neon tetra, Black Neon Tetra (1.6 inches), Glowlight Tetra (1.6 to 2 inches), Diamond Tetra (2 inches), Rummynose Tetra, and Black Phantom Tetra (1.8 inches) can do extremely well in a 20-gallon tank.



Harlequin Rasboras (source)

Rasboras are arguably the best type of fishes for small community tanks.

These fishes 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 (2 inches).

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



Zebra Danios (wikipediaCC BY-SA 4.0)

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 take this into consideration when stocking up your aquarium. Other Danios you can keep in a 20-gallon tank include Danio Marginatus, Pearl Danio, and Celestial Pearl Danio.

Cory Catfish


Corydoras Catfish

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

Since they are timid, it’s advisable to keep them in shoals of three (or above). What’s more, these freshwater catfish aren’t aggressive at all, though they prefer soft, acidic water.

Furthermore, catfish are extremely cute and can awe even the toughest hearts.



Tiger Barb (sourceCC BY-SA 4.0)

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

They are so active that you should only keep them with tank mates who can tolerate boisterous companions. Additionally, barbs prefer living in schools of at least five members on top of soft acidic water that’s cool and well-aerated.

Take note that 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.


Gourami Fish

Gourami Fish

In addition to being easy to keep, Guaramis are quite hardy fish.

Currently, there are over 130 recognized species of Guaramis, with most of them showing parental care to their young ones. Not to mention that these fish often reside at the top of an aquarium.

Since some Guaramis can grow to large sizes, it’s advisable that you go for small-sized species like the Thick-lipped Guaramis (3.5 inches), Dwarf Guaramis (3.5 inches), and the Banded Guaramis (4.7 inches).



Ram Cichlid

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

In fact, there are many types of cichlids out there such as: angelfish, dwarf cichlids, ram cichlids, discus fish, oscar fish, etc. From the ennumarated fish species, only ram and dwarf cichlids should be kept in 20 gallon aquariums.

Angelfish, discus fish and oscars can get pretty big, and quickly outgrow a 20 gallon fish tank.

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


Cherry Shrimp

Cherry Shrimp

Many freshwater shrimps originate from the regions of eastern Asia, except the Ghost Shrimp, which comes from the southern Unites States.

Aquarium shrimp can add a fun element to your tank because they come in a range of sizes and colours. 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. These fishes 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 fishes also moult as they grow, which makes them shed exoskeletons from time to time.


Betta Fish

Betta Fish

Betta fish also known as the Siamese Fighting Fish are usually 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 stays at the top of 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.

Stocking Ideas for Your 20-Gallon Fish Tank

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

Also not all of them can live happily together. As such, it’s important to know the species to include together and which ones to leave out. Here are several examples of freshwater fish combinations you can try out:

Stocking Idea #1

  • 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.

Stocking Idea #2

  • 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

Stocking Idea #3

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

Stocking Idea #4

  • 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

Stocking Idea #5

  • 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)

Stocking Idea #6

  • The Eye Catcher: 10 Danio Margaritatus
  • Additional Stocking: 6-8 Corydoras

Stocking Idea #7

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

Stocking Idea #8

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

Stocking Idea #9

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

Stocking Idea #10

  • 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 in a ratio of ‘one 1-inch fish per every gallon of water. This means that a 20-gallon tank can hold should accommodate about twenty 1-inch fishes. Always take into account the size of the fish species before stocking up.

Also, ensure that your aquarium environment fits the species of fish you want to bring in. Some tanks have water heaters and others don’t, which can be risky depending on the type of species you buy. For instance, most tropical fish can only do well in water that’s around 78 degrees in temperature.

You may need to invest in a thermometer and heater if you reside in an area with a cold climate.

Fishkeeping   Updated: November 6, 2019
avatar Hello, my name is Fabian, and I am the Chief Editor at Aquarium Nexus. I have over 20 years of experience in keeping and breeding fish. The aquarium hobby brings me immense joy, and I take great pleasure in sharing my experiences with others.

Questions and Answers

Dwain Bankston April 7, 2020 Reply

I have 1 guarmai i have some artificial plants will add some live plants soon this is in a 20gal standard with regular filter plus a sponge filter what can i add and how many fish also what do you recommend plant wise thanx

Fabian, I have a question when you talk about stocking a tank you list The eye catcher, the swarm, and ground level. If I picked stocking idea 1, do I stock the eye catcher, warm and ground level?


Are the Honey Gourami interchangeable with other Gourami species? Ie could I use Blue Gourami in stocking idea #5?

    Yes, most small gouramis will work. You should not choose kissing gourami or giant gourami, because they will grow to a big size.

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