25 Freshwater Fish Species That Are Best for 20-Gallon Fish Tank

Starting a freshwater fish tank can be a fun and rewarding hobby, but choosing the right fish species to inhabit your tank can be a daunting task.

With so many options available, it can be difficult to know which species will thrive in your specific tank. In this article, we will take a closer look at 25 freshwater fish species that are perfect for a 20-gallon tank.

From brightly colored tetras to peaceful catfish, these fish will add beauty and diversity to your tank, while also being relatively easy to care for.

Whether you’re a seasoned aquarist or a first-time fishkeeper, this list will provide you with plenty of options to choose from. So, let’s dive in and explore the best freshwater fish species for a 20-gallon tank!

Neon Tetra

The Neon Tetra (Paracheirodon innesi) is a small and brightly colored freshwater fish that is a popular choice among aquarists.

These fish are native to the tributaries of the Amazon River in South America and typically grow to be around 1.5 inches in length.

They are known for their vibrant colors, with a bright neon blue stripe running along the top of their bodies and a red stripe along the bottom.

Neon Tetras are relatively hardy and easy to care for, making them a great option for beginner fish keepers. They are also known for being peaceful and social, making them a great addition to community tanks.

However, It’s important to keep in mind that they require a well-maintained aquarium with good water conditions, including a pH between 6.0-7.0 and a temperature between 72-82F.

Guppy Fish

The Guppy fish (Poecilia reticulata) is a small, colorful freshwater fish that is popular among both beginner and experienced aquarists. They are native to the northeast coast of South America and typically grow to be around 2 inches in length.

Guppies are known for their vibrant colors and patterns, which can range from solid hues to multicolored and even metallic scales.

They are hardy fish that are easy to care for and can adapt to a wide range of water conditions. They are also considered livebearers which means they give birth to live fry and not eggs.

Guppies are generally peaceful and can thrive in community tanks, but males can be territorial, so it’s best to keep them in groups of females or one male to several females.

They are also known for being good at reproducing and can be a good choice for breeding projects.

Betta Fish

Read our complete Betta fish guide here!

Betta fish, also known as Siamese Fighting Fish, is a popular species of freshwater fish known for their vibrant colors and long fins. They are native to Southeast Asia and typically live in stagnant or slow-moving water.

Bettas are known for their aggressive behavior towards other males of the same species, hence the name “Siamese Fighting Fish.”

They can be kept in small bowls or tanks, but it is important to ensure they have adequate space and water conditions. Bettas are also popular in the fishkeeping hobby and can be found in many different colors and patterns.

Zebra Danio

Read our complete Zebra Danio care guide here!

The Zebra Danio Fish, also known as Danio rerio, is a small freshwater fish that is native to the Ganges River in India. They are a popular species for aquarists due to their hardiness, small size, and bright coloration.

Zebra Danios are a hardy species that can tolerate a wide range of water conditions and temperatures. They are also active and schooling fish and they tend to be more comfortable when kept in groups.

They are known to breed easily in captivity, which makes them a great species for beginners to breeding fish. They reach a maximum size of about 2.5 inches and can live for up to five years.

Cherry Barb

Read the complete Charry Barb care guide here!

The Cherry Barb, also known as Puntius titteya, is a small freshwater fish that is native to Sri Lanka. They are a popular species for aquarists due to their vibrant red coloration and peaceful nature.

Cherry Barbs are hardy fish that can tolerate a wide range of water conditions and temperatures. They are best kept in groups of six or more and do well in planted aquariums.

They have a relatively peaceful temperament and make a great addition to community tanks. They reach a maximum size of about 2 inches and have a lifespan of around 5 to 7 years.

They are also easy to breed and are known to be great parents. They are also known to be great beginner fish species.

Platy Fish

The Platy Fish, also known as Xiphophorus maculatus, is a small freshwater fish that is native to Central America. They are a popular species for aquarists due to their hardiness and bright coloration.

Platies come in a variety of colors and patterns, including red, orange, yellow, and blue. They are hardy fish that can tolerate a wide range of water conditions and temperatures.

They are active and peaceful fish that do well in groups. They are known to breed easily in captivity, which makes them a great species for beginners to breeding fish.

They reach a maximum size of about 2.5 inches and have a lifespan of around 2 to 3 years. They are great community fish and can coexist with a variety of other peaceful species.

Swordtail Fish

Read our complete Swordtail Fish care guide here!

The Swordtail Fish, also known as Xiphophorus helleri, is a small freshwater fish that is native to Mexico and Central America.

They are a popular species for aquarists due to their hardiness, active behavior, and bright coloration. Swordtails are known for their distinctive sword-like extension on the lower part of their tail fins, which gives them their name.

They come in a variety of colors and patterns, including red, orange, yellow, green, and black. They are hardy fish that can tolerate a wide range of water conditions and temperatures.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 4.5 inches and have a lifespan of around 3 to 5 years.

They are also known to breed easily in captivity, which makes them a great species for beginners to breeding fish.

Molly Fish

The Molly Fish, also known as Poecilia sphenops, is a small freshwater fish that is native to Mexico and Central America.

They are a popular species for aquarists due to their hardiness and bright coloration. Mollies come in a variety of colors and patterns, including black, silver, gold, and multicolored.

They are hardy fish that can tolerate a wide range of water conditions and temperatures but prefer water with a pH between 7.0 to 8.0, and a temperature between 72 to 82 degrees Fahrenheit.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 4 inches and have a lifespan of around 3 to 5 years.

They are also known to breed easily in captivity, which makes them a great species for beginners to breeding fish.

Freshwater Shrimp Species

Read our complete Amano Shrimp care guide here!

There are many different species of freshwater shrimp that are popular among aquarists. Some of the most common species include the Red Cherry Shrimp, Ghost Shrimp, and Amano Shrimp.

These shrimp are known for their hardiness, ease of care, and ability to help control algae in the tank. They typically do well in a variety of water conditions and temperatures and are considered to be peaceful, non-aggressive species.

They are often kept in community tanks with other small fish and invertebrates. They can also be kept in planted tanks. These shrimps usually reach a size of about 2-3 inches and have a lifespan of around 2-3 years.

They are also known to breed easily in captivity and can be a great addition to a freshwater aquarium.

Corydoras Catfish

Read our complete Corydoras Catfish care guide!

Corydoras Catfish, also known as Corys, are a group of small freshwater fish that is native to South America.

They are popular among aquarists due to their hardiness, peaceful nature, and the fact that they are bottom feeders that help keep the tank clean.

Corys come in a variety of colors and patterns, including bronze, green, and albino. They are active and peaceful fish that do well in groups, and they are known to be good community fish.

They are best kept in a group of at least 3 to 5 individuals. They reach a maximum size of about 2 to 4 inches and have a lifespan of around 5 to 7 years. They are also known to be great beginner fish species and are easy to care for.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species.

Khuli Loach

Read our complete Kuhli Loach care guide!

The Kuhli Loach, also known as Pangio kuhlii, is a small freshwater fish that is native to Southeast Asia. They are a popular species for aquarists due to their peaceful nature, hardiness, and unique appearance.

Khuli Loaches have slender, eel-like bodies and are typically a light brown color with dark brown spots. They are active and peaceful fish that do well in groups, and they are known to be good community fish.

They reach a maximum size of about 3 inches and have a lifespan of around 5-7 years. They are best kept in a group of at least 4-6 individuals and are known to be easy to care for.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species. They are also known to be great algae eaters and can help keep the tank clean.

Harlequin Rasbora

Read our complete Harlequin Rasbora care guide!

The Harlequin Rasbora, also known as Trigonostigma heteromorpha, is a small freshwater fish that is native to Southeast Asia. They are a popular species for aquarists due to their hardiness, peaceful nature, and bright coloration.

Harlequin Rasboras are known for their distinctive red and black coloration and are considered to be one of the most colorful species of the Rasbora family.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 1.5 inches and have a lifespan of around 5-7 years.

They are best kept in a group of at least 6-8 individuals. They are also known to be easy to care for and can adapt to a variety of water conditions and temperatures.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species.

Endler’s Livebearer (Guppy Fish)

Read our complete Guppy Fish care guide!

The Endler’s Livebearer, also known as Poecilia wingei, is a small freshwater fish that is native to Venezuela. They are a popular species for aquarists due to their hardiness, peaceful nature, and bright coloration.

Endler’s Livebearers are known for their vibrant coloration and can be found in a variety of colors such as red, orange, yellow, and green. They are similar in appearance to Guppies, but are smaller in size and have a shorter lifespan of about 2-3 years.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 1.5 inches and are best kept in a group of at least 6-8 individuals.

They are also known to be easy to care for and can adapt to a variety of water conditions and temperatures. They are also known to breed easily in captivity and can be a great addition to a freshwater aquarium.

Rosy Barb Fish

Read our complete Rosy Barb care guide!

The Rosy Barb is a popular tropical freshwater fish known for its vibrant pink color. It is a member of the Cyprinidae family and is native to the rivers and streams of South Asia.

The fish can grow up to 6 inches in length and can live up to 8 years. They are relatively hardy and easy to care for, making them a great choice for beginners.

They are also active and sociable and can be kept in a community tank with other peaceful fish. The Rosy Barb is an omnivore and can be fed a variety of foods, including flakes, pellets, and live or frozen foods.

Otocinclus Catfish

Read our complete Otocinclus Catfish care guide!

The Otocinclus Catfish, also known as Otocinclus vittatus, is a small freshwater fish that is native to South America. They are a popular species for aquarists due to their hardiness, peaceful nature, and unique appearance.

Otocinclus Catfish have a small, round body and are typically a brown color with dark spots. They are active and peaceful fish that do well in groups, and they are known to be good community fish.

They reach a maximum size of about 1.5 inches and have a lifespan of around 3-5 years. They are best kept in a group of at least 4-6 individuals and are known to be easy to care for.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species. They are also known to be great algae eaters and can help keep the tank clean.

Otocinclus are sensitive to water quality, so it’s important to keep the water clean and well-filtered.

Opaline Gourami

Read our complete Opaline Gourami care guide!

The Opaline Gourami is a species of freshwater fish that belongs to the Osphronemidae family. It is native to Southeast Asia and is known for its unique iridescent blue, silver, and orange coloration.

The fish can grow up to 6 inches in length and can live for several years with proper care. They are relatively peaceful and can be kept in a community tank with other non-aggressive fish.

They are also known to be hardy, and easy to care for, making them a great choice for beginners. The Opaline Gourami is an omnivore and can be fed a variety of foods, including flakes, pellets, and live or frozen foods.

They are also known for their labyrinth organ that allows them to breathe air, which makes them a unique addition to any aquarium.

Cardinal Tetra

Read our complete Cardinal Tetra care guide!

The Cardinal Tetra Fish, also known as Paracheirodon axelrodi, is a small freshwater fish that is native to South America, specifically the tributaries of the Orinoco and the upper Amazon River.

They are a popular species for aquarists due to their bright coloration, hardiness, and peaceful nature. Cardinal Tetras are known for their distinctive red and blue coloration and are considered to be one of the most colorful species of the Tetra family.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 1.5 inches and have a lifespan of around 4-5 years.

They are best kept in a group of at least 6-8 individuals.

They are also known to be easy to care for and can adapt to a variety of water conditions and temperatures but prefer water with a pH between 6.0 to 7.0 and a temperature between 72 to 82 degrees Fahrenheit.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species.

Rummy Nose Tetra

Read our complete Rummy Nose Tetra care guide here!

The Rummy Nose Tetra, also known as Hemigrammus rhodostomus, is a small freshwater fish that is native to South America, specifically the Orinoco and the upper Amazon River.

They are a popular species for aquarists due to their bright coloration, hardiness, and peaceful nature.

Rummy Nose Tetras are known for their distinctive red and white coloration, particularly the distinctive red coloration on their nose, which gives them their name.

They are active and peaceful fish that do well in groups, and they are known to be good community fish. They reach a maximum size of about 1.5 inches and have a lifespan of around 5-7 years. They are best kept in a group of at least 6-8 individuals.

They are also known to be easy to care for and can adapt to a variety of water conditions and temperatures but prefer water with a pH between 6.0 to 7.0 and a temperature between 72 to 82 degrees Fahrenheit.

They are also known to be a great addition to a community tank and can coexist with a variety of other peaceful species.

Glowlight Tetra

Read our complete Glowlight Tetra care guide!

The Glowlight Tetra (Hemigrammus erythrozonus) is a small, freshwater fish that is native to South America. They are known for their distinctive silver and orange coloration, and their name comes from the iridescent “glow” that they give off.

They are a popular choice for home aquariums because of their small size and peaceful nature. They are best kept in groups and prefer a well-planted tank with a dark substrate to bring out their colors.

They are also relatively hardy fish that can adapt to a wide range of water conditions. Overall, the Glowlight Tetra is an attractive and easy-to-care-for addition to any community aquarium.

Celestial Pearl Danio (Galaxy Rasbora)

Read our complete Galaxy Rasbora care guide!

The Celestial Pearl Danio (Danio margaritatus) is a small, freshwater fish that originates from Myanmar. They are known for their vibrant, iridescent coloration, with striking blue and purple hues on their fins and bodies.

They are one of the smallest fish in the Cyprinidae family and are best kept in groups in a well-planted tank with a dark substrate to bring out their colors. These fish are relatively hardy and can adapt to a wide range of water conditions.

Celestial Pearl Danios are peaceful and active fish that can make a beautiful addition to any community aquarium. They are also known as Galaxy Rasbora and Microrasbora sp. “Galaxy”.

They are very sensitive to water parameters and require a high level of care, so they are not recommended for beginner aquarists.

German Blue Ram

Read our complete German Blue Ram care guide!

The German Blue Ram, also known as the Ram Cichlid, is a small, brightly colored freshwater fish that is native to South America. It is a member of the Cichlidae family and is known for its striking blue and yellow coloration.

These fish are relatively small, reaching a maximum size of around 2.5 inches in length. They are peaceful and can be kept in a community tank with other non-aggressive fish.

They are also known to be hardy and easy to care for, making them a great choice for beginners. German Blue Ram is an omnivore and can be fed a variety of foods, including flakes, pellets, and live or frozen foods.

They are also known to be sexually dimorphic, which means that males and females have different physical characteristics and are easy to distinguish.

Dwarf Gourami

Read our complete Dwarf Gourami care guide!

Dwarf Gourami fish is a species of freshwater fish that belongs to the gourami family. They are known for their vibrant colors, which can range from blue to orange.

They are small in size, usually growing to a maximum of 2 inches in length. They are native to the freshwater rivers and streams of India and Bangladesh.

Dwarf Gourami is typically a peaceful fish and can be kept with other small community fish. They are also popular in the aquarium trade and are easy to care for, making them a good choice for beginners.

White Cloud Mountain Minnow

Read our complete Mountain Minnow care guide!

White Cloud Mountain Minnow is a species of freshwater fish that belongs to the Cyprinidae family. They are native to the White Cloud Mountain region of China.

They are small fish, growing to a maximum size of about 2 inches in length. They are known for their bright silver coloration with a greenish-blue iridescent sheen.

They are hardy and adaptable fish that can tolerate a wide range of water conditions. They are also active swimmers and make a great addition to a community tank.

They are popular among aquarium enthusiasts because of their bright colors and peaceful nature, making them a good choice for beginners.

Golden Wonder Killifish

Read our complete Goldern Wonder Killifish care guide!

Aplocheilus lineatus, also known as the Golden Wonder Killifish or Spotted Killifish, is a species of freshwater fish that is native to India and Sri Lanka.

It is a member of the Aplocheilidae family and is known for its bright orange-gold coloration and black spots on its body.

These fish typically reach a length of around 2 inches and are popular among aquarists for their striking coloration and hardiness. They are relatively easy to care for and can be kept in a variety of water conditions.

They are also known for their peaceful nature and can be kept with other fish species.

Boesemani Rainbow Fish

Read our complete Boesemani Ranbowfish care guide!

Boesemani Rainbow Fish (Melanotaenia boesemani) is a species of freshwater fish that is native to the island of New Guinea.

It is a member of the Melanotaeniidae fish family and is known for its vibrant coloration that can range from blue to green to red. These fish typically reach a length of around 3 to 4 inches.

These Rainbowfish species are popular among aquarists for their striking coloration, peaceful nature, and hardiness. They are relatively easy to care for and can be kept in a variety of water conditions.

They are also known for their active and lively behavior, making them a great addition to a community tank. They are also known to be great for breeding in captivity and the fry is quite easy to raise.

Conclusion

In conclusion, a 20-gallon fish tank can provide a great home for a variety of freshwater fish species.

From the vibrant Neon Tetra to the peaceful Otocinclus Catfish, these 25 fish species are all great options for the beginner or experienced fish keeper.

Remember that when it comes to fish compatibility, not all fish species get along, so it is essential to research the specific requirements and behavior of each fish species before making a purchase.

With proper care and maintenance, your 20-gallon tank can be a beautiful and thriving ecosystem for your new fish friends. Happy Fish Keeping!