Nano Aquarium Fish Guide


Nano aquariums are unique because they are small in size. Therefore, it is important to select the right fish to inhabit these small environments. Not all fish will thrive in nano tanks, so it is important to stock it with the right type of fish. Just as you would when setting up a larger tank, setting up a nano tank requires some planning as well.

While the small size may seem like a limitation, there is actually a huge variety of fish that thrive in nano aquariums. Some of these fish are very hardy fish that do not require specialized care. Perhaps, they are more suitable for a beginner. Other species of fish require a bit more care and attention. However, all of these fish share a common characteristic. They are all small fish that thrive in nano aquariums.

Nano Aquarium Fish

What Type of Fish Can I Keep in a Nano Aquarium?

There are many different species of fish that you can keep in a nano aquarium. Fish that are great for nano aquarium include fish such as, Betta fish, Neon tetra, Cardinal tetra, Sparkling gourami, Chili rasbora, Harlequin rasbora, and Oto cats. These are all small fish that thrive in a small environment.

As an obvious, smaller species of fish are generally better suited for your nano tank. However, not all small fish are suitable for nano tanks. While it may seem like the type of fish you can keep in a nano tank is very limited, this is not the case at all. There are many small yet awesome fish that can be added to a nano tank. Keep in mind that this is not a complete list. There are many fish species that are not included in this list, but can be kept in a nano aquarium. With that said, here is a short list of some of the best fish to keep in a nano aquarium.

Awesome Fish for 10 Gallon Aquariums #shorts

Bettas Fish (Betta splendens)

We will start this list with one of the most popular fish in the aquarium hobby.

Betta fish originate in marshes and other shallow bodies of water throughout Thailand. They do not swim very fast, and they prefer slow moving water. The male fish are territorial, and they will establish itself to a specific area of the tank. Naturally, this makes betta fish an awesome candidate for a nano aquarium.

Male betta fish can be very territorial and have an aggressive temperament. Therefore, it is ideal to house one male betta in each nano aquarium. Female bettas can be housed together in larger sorority tanks.

Betta fish come in many different colorations and fin types, and they are absolutely beautiful. 

  • Size: 5.7cm
  • Tank size (minimum): 5 Gallons
  • Care level: easy
  • Water Temperature: 75° – 81° F
  • pH: 6.5 – 7.5
  • Diet: Carnivore

Neon Tetra (Paracheirodon innesi)

Neon Tetras are one of the most popular fish in the aquarium trade. Many consider them a classic to the fishkeeping hobby. In fact, they were discovered as early as 1934. They are thin bodied fish with small fins. They have a bright blue head tapering off to a red tail.

They are native to the Amazon River basin. In the wild, they can shoal in numbers reaching many thousands. In an aquarium setting, they should be kept in numbers of 6 or more.

  • Size: 3cm
  • Tank size(minimum): 10 Gallons
  • Care level: easy
  • Water Temperature: 72° – 76° F
  • pH: 6.0 – 7.0
  • Diet: Omnivore

Cardinal Tetras (Paracheirodon axelrodi)

Cardinal Tetra are very similar in appearance to Neon Tetras. In fact, they are closely related.

While they are very similar, but there are some differences. Cardinal Tetra can grow to almost double the size of the Neon Tetra. In addition, Cardinal Tetra have blue and red stripes which extend the entire length of their bodies. While they are different, it is no surprise that they are often mistaken for each other, especially as juveniles.

Cardinal Tetras are also shoaling fish, and they should be kept in groups of six or more.

  • Size: 5cm
  • Tank size(minimum): 15 Gallons
  • Care level: easy
  • Water Temperature: 72° – 76° F
  • pH: 6.0 – 7.0
  • Diet: Omnivore

Sparkling Gourami (Trichopsis pumila)

Sparkling gourami is a small fish with a beautiful sparking appearance. They have almost translucent fins which also carry rows of metallic speckles. During breeding season, their fins will get edged in red, and the blue coloration on their body intensifies.

A nano aquarium setup with slow moving water and plenty of plant for cover would be ideal. They are very peaceful fish, and they do very well with other peaceful fish of similar size.

One interesting fact about sparkling gouramis is that they make a croaking sound, which intensifies during mating season.

  • Size: 3.8cm
  • Tank size(minimum): 10 Gallons
  • Care level: moderate
  • Water Temperature: 76° – 82° F
  • pH: 6.0 – 7.0
  • Diet: Omnivore

Chili Rasbora (Boraras brigittae)

Chili Rasbora is a stunning looking fish that is native to Borneo. They are sometimes known as mosquito rasboras. They are a tiny red fish with a black stripe down each side that tapers as it nears the tail.

Chili Rasboras are shoaling fish, and they are most comfortable when kept in groups of six or more. They are active fish, and will make a great addition to a planted nano aquarium.

  • Size: 2cm
  • Tank size (minimum): 5 Gallons
  • Care level: easy
  • Water Temperature: 68° – 78° F
  • pH: 5.0 – 7.0
  • Diet: Carnivore

Harlequin Rasboras (Trigonostigma heteromorpha)

Harlequin Rasboras are orange-red fish with a silver underbelly and a black marking that runs from the dorsal fins to its tails. This is one of the most stunning looking fish when kept in a small shoal of six or more. 

  • Size: 5cm
  • Tank size(minimum): 10 Gallons
  • Care level: easy
  • Water Temperature: 72° – 81° F
  • pH: 6.0 – 7.5
  • Diet: Omnivore

Oto Cats (Otocinclus affinis)

Oto cats, or Otocinclus Catfish, are peaceful dwarf catfish. They have a silver coloured body with a black stripe running the length of it. As shoaling fish, they are most comfortable when kept in groups of five or more.  

Oto cats are great because they keep the algae growth in check. They will eat the soft algae off the aquarium glass, plants, and other surfaces throughout the tank. In a small nano tank, they can run out of algae to feed on rather quickly. As herbivores, they will readily feed on algae wafers. In addition, they may feed on green vegetables such as lettuce, spinach and zucchini.  

  • Size: 5cm
  • Tank size(minimum): 10 Gallons
  • Care level: easy
  • Water Temperature: 72° – 82° F
  • pH: 6.0 – 7.5
  • Diet: Herbivore

Other Awesome Fish for Nano Aquariums

We’ve highlighted some of the best fish for nano aquariums. However, this is by no means a comprehensive list. There are many other fish species that can thrive in small aquariums. If you wish to further your research, we recommend looking into the following fish species:

The possibilities of a nano aquarium is endless. Keep in mind that the fish that you keep is only one aspect of your nano tank setup. In fact, the tank decoration and aquascaping of your nano tank can change the entire look and feel of the same tank. Keep in mind that nano tanks are popular for keeping invertebrates such as shrimp and aquatic frogs as well.

While there are many different potential options, keep in mind that you much choose one, or just a few. After all, this is a nano aquarium, and you are working with a small environment. Overcrowding can lead to an unhealthy environment very quickly.

How Many Fish Can I Keep in a Nano Tank?

When considering how many fish to keep in a nano tank, the general guideline is to stock only one inch of fish per one gallon of water.

The stocking level of fish is an important consideration for a nano aquarium. Space is limited, so it can easily get overcrowded. A few extra fish over capacity in a large tank may not be a big deal. However, every fish impacts the water chemistry in a nano tank.

The general guideline of one inch of fish per one gallon of water, is an effective method of estimating an aquarium’s capacity. However, keep in mind that the actual capacity of an aquarium can differ based on many factors. The most significant factor is the actual fish that is being kept. Different fish produce different amounts of waste. Another factor that determines the aquarium’s capacity is the filtration system in your nano aquarium. A nano tank with an effective filtration system will be able to support more fish. Therefore, having a good filtration system that is properly maintained is important. Live plants may also contribute to better water quality.

How Many Fish Can You Keep in a 10 Gallon Aquarium Tank? #shorts

When adding fish to a nano tank, do so carefully and slowly. Cycle the aquarium for at least a few weeks, and allow the water parameters to stabilize. Once the aquarium is cycled properly, add a few fish into the aquarium. Observe the fish and make sure they are healthy. Measure the water parameters and make sure it is stable and falls within a healthy range. If you feel that the nano aquarium can support more fish, add a few more fish carefully and slowly. When in doubt, stock lean. It is always better to keep less fish than the aquarium’s maximum capacity.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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