Fish Types

Top 10 Small Freshwater Fish for Small Aquariums

Small Freshwater Fish

Keeping is a small fish tank is a hobby enjoyed by both beginners and experienced aquarists. After all, small aquariums are convenient, cheap to set up, and have very minimal space requirements.

However, one of the most common problems when it comes to these aquariums is determining which types of fish would thrive in such a space-restricted environment.

So, whether you are setting up your own small aquarium or are looking to add more nano inhabitants to your tank, you need to know which types of freshwater species are best suited for your needs.

Here are our top 10 picks for the best freshwater fish for small tanks:

1. Betta

Betta Fish
  • Experience level: Beginner to intermediate
  • Max size: 3 inches
  • Temperament: Peaceful (under certain conditions)
  • Water temperature: 75-86°F
  • Water pH: 6.8-7.4
  • Aquarium hardiness: Hardy
  • Min tank size: 2 gallons

Also known as the Siamese fighting fish, the betta fish is a tropical fish species that can only grow up to 3 inches in length. With a max size of 3 inches, bettas are among the smallest freshwater fish and make convenient aquarium pets. They can be housed in a small bare-bottom tank with at least 2 gallons of water.

Male bettas feature vivid coloration and long flowing fins, whereas female bettas are less colored and have relatively shorter fins. Their beautiful appearance gives them amazing aesthetic appeal.

They have a hardy disposition, so they’ll have no trouble tolerating poor water quality, varying water temperatures, and cramped up spaces. They will, however, require regular water changes.

While bettas are peaceful species by nature, you should never put two males in the same aquarium due to their tendency to fight each other. On the other hand, multiple female bettas have no trouble living together and can be kept in the same tank with one male betta.

2. Celestial Pearl Danios

Celestial Pearl Danios


  • Experience level: Beginner
  • Max size: 1 inch
  • Temperament: Peaceful schooling fish
  • Water temperature: 73-79°F
  • Water pH: 6.5-7.5
  • Aquarium hardiness: Hardy
  • Min tank size: 10 gallons

If you’re looking for a small freshwater fish that can boost your aquarium’s aesthetic value, check out the celestial pearl danios.

The celestial pearl danio is a freshwater fish that boasts a beautiful appearance and comes in a range of interesting colors. They are a popular aquarium fish because of their size, peaceful temperament, and hardy disposition.

The distinguishing characteristics between the male and female species of the fish are bountiful. But perhaps the most interesting one is with their appearance, as male danios are smaller and more colorful than their female counterparts.

Adult danios are small and can only reach a maximum length of 1 inch. Due to their compact size, the celestial pearl danio can be kept in a 10-gallon tank, which should be heavily planted to mimic their natural habitat. For best results with this fish, keep the danios in groups of at least 5 or 6 and make sure that there are more females than males.

Celestial pearl danios are omnivores. They will eat everything from algae, plants and brine shrimp to flakes, pellets and live grindal worms.

3. Neon Tetra

Neon Tetra


  • Experience level: Intermediate
  • Max size: 2.5 inches
  • Temperament: Peaceful
  • Water temperature: 70-81°F
  • Water pH: 6.0-7.0
  • Aquarium hardiness: Hardy
  • Min tank size: 10 gallons

The neon tetra is a freshwater tropical fish that can reach up to 2.5 inches in length. However, the average length of the neon tetra is 1.5 inches.

For a fish that grows up to 1.5-2.5 inches long, the neon tetra can be kept in a 10-gallon tank. However, tetras are prone to stress when the size of their school is small, so you should get at least 15-20 tetras and house them in a 20-gallon tank, which is the minimum required for that number of tetras.

When designing their aquatic home, be sure to add plenty of low-light hiding spots in the tank. These creatures are more comfortable living in darker environments, and giving them places where they could hide and rest would be better for them overall.

Neon tetras are peaceful and pleasant fish that will do great in a community tank, given that their tank mates are small and have the same temperament. They are also very low-maintenance pets, which is why they’re popular amongst beginner aquarists.

Neon tetras are omnivores, which means they’ll enjoy eating just about anything.

4. Guppies

  • Experience level: Beginner
  • Max size: 2.5 inches
  • Temperament: Peaceful
  • Water temperature: 66-84°F
  • Water pH: 7.0-8.0
  • Aquarium hardiness: Very hardy
  • Min tank size: 10 gallons

There are lots of reasons why guppies are among the most popular fish species in the fishkeeping world. Above all, they are extremely hardy fish that only requires minimal care from start to finish. Other reasons include their convenient size and their incredibly striking appearance, which comes in unlimited color combinations.

Male guppies can grow for up to 2 inches in length, while female guppies are comparatively larger and tend to grow 2.5 inches long. Since these cute little creatures can grow up to 2-2.5 inches in length, an aquarium with the capacity of at least 10 gallons is recommended for their housing.

Despite not being schooling fish, guppies must be kept in groups of at least 6 or more members. But when grouping guppies together, make sure to keep the ratio of males to females at 1:2 to avoid fighting in the tank. 

If you’re planning to give them tank mates outside of their own species, you should find small- to medium-sized fish species (corydoras, platies, etc.) with a peaceful, non-aggressive temperament.

Guppies are omnivores and will gladly eat live foods, freeze-dried foods, and flake-based aquarium foods.

5. Sparkling Gourami

Sparkling Gourami
  • Experience level: Beginner
  • Max size: 1.6 inches
  • Temperament: Relatively peaceful
  • Water temperature: 71.5-80.5°F
  • Water pH: 6.0-8.0
  • Aquarium hardiness: Hardy
  • Min tank size: 15 gallons

The sparkling gourami is a tiny freshwater aquarium fish that has a maximum size of 1.6 inches and is capable of adapting to various environments, including poor water conditions. With its extremely compact size, the sparkling gourami is a great option for those who are seeking small freshwater fish.

Sparkling gouramis have patterned fins that make up a significant chunk of their elongated bodies. They also feature a small pelvic fin, a merged anal fin, a standing dorsal fin, and striking blue eyes bordered by a thin red line. With their somewhat distinctive appearance, telling apart the sparkling gourami from other small fish is quite easy.

In addition to their incredibly convenient size, sparkling gouramis are peaceful creatures that should be kept in groups of at least five or six, with a recommended ratio of one male for every 3-4 females.

They also won’t cause any trouble when kept in a tank with other fish species. However, in order for everything to work out, their tank mates should have a peaceful temperament and be roughly the same size as them. Some examples of good gourami tank mates are tetras, corydoras, rasboras, and neon rainbowfish.

6. Bumblebee Goby

Bumblebee Goby
  • Experience level: Intermediate
  • Max size: 1.7 inches
  • Temperament: Peaceful
  • Water temperature: 73-79°F
  • Water pH: 6.5-7.5
  • Aquarium hardiness: Hardy
  • Min tank size: 10 gallons

The bumblebee goby is a small and peaceful fish species that features a bright yellow body and tar dark stripes. It got its name from its resemblance to one of nature’s most industrious and important animals: bees.

Adult bumblebee gobies can reach up to 1.7 inches in length and must be kept in a tank with a capacity of at least 10 gallons. Since gobies are group fish, they should be kept in groups of at least 6-7 members of the same species.

Bumblebee gobies are very active swimmers, and their tank should have enough floor space to accommodate their knack for swimming. They also love to hide, so it’s a good idea to provide a sandy substrate, live plants, river rocks, and driftwood where they can do just that.

Though the bumblebee goby is a hardy fish species, it’s not recommended for beginner aquarists due to their often demanding nature.

7. Dwarf Puffer

Dwarf Puffer


  • Experience level: Intermediate
  • Max size: 1 inch
  • Temperament: Territorial/aggressive
  • Water temperature:72-79°F
  • Water pH: 6.5-7.5
  • Aquarium hardiness: Not hardy, very salt intolerant
  • Min tank size: 10 gallons

Dwarf puffers are a relatively new fish in the aquarium hobby scene. They are a freshwater fish species that thrives in more pleasant environments, so they should never be placed in brackish or saltwater tank. 

Adult dwarf puffers can only grow up to 1 inch long, making them one of the smallest aquarium fish in the world. Their very small size means that they don’t need big tanks, but you should still give them a tank with a capacity of at least 10 gallons.

When setting up a tank with a group of dwarf puffers, the ideal tank setup is 10 gallons for the first puffer and 5 gallons for every additional puffer. This is because dwarf puffers, despite their small size, are territorial fish species that require lots of personal space. Giving them enough room in the tank will help lower their aggression.

In addition, adding lots of plants and rocks to their tank is highly recommended because creating more hiding places can help keep their stress levels down.

8. Ember Tetra

Ember Tetra
  • Experience level: Beginner
  • Max size: 1 inch
  • Temperament: Peaceful
  • Water temperature: 68-82°F
  • Water pH: 5.5-7.0
  • Aquarium hardiness: Relatively hardy
  • Min tank size: 10 gallons

The ember tetra is a nano freshwater fish that got its name from its bright orange color which resembles the glow of dying fire. This fish species is easily identifiable because of its blazing hot appearance.

Ember tetras are very small and can grow up to 1 inch long as adults. However, the standard size of ember tetras is around 0.8 inches long.

Though ember tetras are smaller than most fish species, they are active swimmers that love to hang out in the middle section of a tank and hide in plants and rocks. So if you want to keep them happy, they should be kept in at least a 10-gallon tank with lots of hiding places.

Ember tetras are relatively hardy fish species that can adapt to a range water hardness and pH levels. They will, however, be affected by poor water quality and fluctuations.

When it comes to their diet, ember tetras are omnivorous fish species that will eat flakes, pellets, and live foods, among others. Give them a diverse diet so they’ll remain in good shape.

9. Salt and Pepper Catfish

Salt and Pepper Catfish
  • Experience level: Beginner to intermediate
  • Max size: 1.4 inches
  • Temperament: Peaceful
  • Water temperature: 72-79°F
  • Water pH: 6.2-7.2
  • Aquarium hardiness: Hardy
  • Min tank size: 8 gallons

One of the three pygmy corydoras species, the salt and pepper catfish is a small freshwater species characterized by its light tan body plastered with black and gray patches and stripes. This fish species is one of the most common aquarium fish in the world.

Adult salt and pepper catfish can reach a maximum length of 1.4 inches, with female species often growing larger than males. They are schooling fish and must be kept in a school of at last six members to thrive. The minimum tank size required for the recommended number (6) of salt and pepper catfish is 8 gallons.

Though salt and pepper catfish are hardy and adaptable to different types of water conditions, they are considered delicate species due to their vulnerability to extremely warm temperatures and poor water quality.

Salt and pepper catfish are omnivores with a diet consisting of frozen foods, micro pellets, smaller flakes, small crustaceans, and wafer foods, among others. They are also scavengers that love to scour the bottom of the tank for any leftover food.

10. Least Killifish

Least Killifish


  • Experience level: Beginner
  • Max size: 1.4 inches
  • Temperament: Peaceful
  • Water temperature: 66-75°F
  • Water pH: 7.0-8.0
  • Aquarium hardiness: Hardy species
  • Min tank size: 5 gallons

The least killifish is one of the smallest freshwater fish species out there. It is also the smallest livebearer in the world, meaning that it has internal fertilization and gives birth to live young.

This live-bearing fish species can grow up to 1.4 inches in length, with males (0.75 inches) being significantly smaller than females (1.4 inches). With a maximum length that ranges from 0.75 - 1.4 inches, the least killifish is among the best fish for 5 gallons tank and can be kept in fairly large groups.

In addition, their 5-gallon tank setup should have a gentle filtration system and a vast collection of plants.

Least killifish are peaceful creatures with an omnivorous diet. For optimum health, they should be given a varied diet which includes vegetables and live and frozen foods.


One of the best parts about owning a small freshwater aquarium is that it’s as enjoyable as owning a large freshwater tank. Another thing that’s great about it is having the freedom to select the type of fish you want to live in it, despite the options being somewhat limited.

Just remember that even if your freshwater aquarium is small, it still needs to be given regular care and maintenance. Its tiny little inhabitants also need to be properly fed and given enough space for them to thrive.

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