What Are the Best Fish for A Nano Tank (12 Best Fish)

Best Fish for A Nano Tank

Here’s a list of the best fish for nano tanks, along with two non-fish aquatic tank mates to consider.

You’ll also find a list of stocking ideas, fish to avoid, what you should consider before you buy a tank, and a few other helpful tips.

All these fish are hardy and need at least a 10-gallon tank to be happiest except for bettas.


1. Betta Fish (Needs a Heater)

With their beautiful colors and magnificent tails, Bettas are popular for small tanks. Bettas are also known as Siamese fighting fish because of the notorious gladiatorial combats between males. 

Just because you’ve seen bettas in tiny tanks without heat doesn’t mean it’s ideal. You’ll want at least a 3-gallon heated tank for the happiest betta.

While you can’t keep multiple male fish in a tank, you can keep a female betta fish sorority tank with multiple female bettas. Sorority tanks have 4-5 females minimum and ten maximum, with the smallest recommended aquarium size being 20-30 gallons. 

You can keep bettas in community tanks. However, they can be feisty, so have an exile tank ready if things don’t work out.

  • Maximum size: 2.5 (females) to 3.0 inches (males)
  • Temperature: 72°-86°F

2. Endler Guppies (Best Fish for a Small Bowl)

Male Endler guppies are some of the prettiest guppies. They come in a variety of intense colors, rivaling bettas for beauty. Their colors intensify after age six months.

Endler guppies are prolific breeders and often hybridize with other guppies. They give birth every 23 days, so keep that in mind before adding males and females to the same small tank. 

You’ll find that Endler guppies are relatively undemanding and easy to keep. 

  • Maximum size: 1.0 inch
  • Temperature: 72°-78°F

3. Sparkling Gourami

If you like rainbow colors, sparkling gouramis (pygmy gouramis) are worth consideration. 

Sparkling gouramis need a 10-15 gallon tank with ten more gallons for each additional gourami. They prefer to be in groups of 5-6, which isn’t possible in a nano tank. While they’re generally peaceful, they may compete with other males.

Gouramis have a labyrinth breathing organ as an adult and come to the surface for air. However, they swim at various tank levels. 

  • Maximum size: 1.5 inches
  • Temperature: 76°-82°F

4. Ember Tetras

The electric red-orange color of an ember tetra can make a striking addition to your coldwater nano tank. 

Ember tetras are peaceful fish that usually spend their time in the middle layer of your tank. 

In the wild, their habitats are highly-forested, so they use plants and driftwood to hide. So, a planted tank with driftwood is an ideal habitat.

They’re happiest surrounded by other ember tetras, in schools of at least eight. 

  • Maximum size: 0.8 inches
  • Temperature: 68°-82°F

5. Zebra Danios

Zebra danios (zebrafish) are easy to accommodate and work well in a coldwater community tank. 

Zebra danios have a distinctive horizontal bluish-purple stripe on a silvery-gold body. However, within the species are albino, golden, veil-tailed, leopard, and long-finned varieties.

They’re incredibly active and will spend most of their time toward the top of the tank.

Keep in mind that zebra danios are prolific breeders, so keeping males and females together isn’t ideal for a small tank.

  • Maximum size: 2.5 inches
  • Temperature: 64°-74°F

6. White Cloud Minnows (Easiest Fish to Care for in a Bowl)

White cloud minnows are called the working man’s neon because they look similar while costing less. 

You’ll want to keep your white clouds in schools of six or more. They’re peaceful, so you’ll want to avoid larger, more aggressive tank mates that think you’re offering them a snack. 

While white clouds aren’t very demanding about water quality, they don’t tolerate heat well. Thus, living in a tank above room temperature will shorten their lifespan considerably.

  • Maximum size: 1.5 inches
  • Temperature: 64°-72°F

7. Pygmy Corydoras

Black-striped pygmy corydoras catfish don’t have a striking appearance on their own, but they have some interesting behaviors that make them intriguing. 

Shoaling is rare for bottom-dwelling catfish, and you may even see them swimming in the middle of the tank, which is even rarer for a bottom-dweller.

You will want to keep a minimum of four, with eight being even better. But, of course, the more you have, the more impressive their schooling activity. 

  • Maximum size: 0.75 (males) to 1.0 inch (females)
  • Temperature: 72°-79°F

8. Pea Pufferfish

Having a tank of pufferfish is like having a tank of puppy dogs. They have so much personality and may even greet you with excitement when you come to the tank. 

Pea puffers are the smallest puffers and are great for nano tanks. 

While you can keep pea pufferfish alone, they do best in groups of at least three. In addition, they need at least a 10-gallon tank and can be territorial, so it’s best to have five gallons of water for each additional fish.

Adding shrimp, snail, crab, and crayfish tank mates keeps their teeth a healthy length–just don’t get attached.

  • Maximum size: 0.98 inches
  • Temperature: 74°-82°F

9. Six-Ray Corydoras

The six-ray corydoras is a bottom-dwelling catfish that prefers a sandy substrate. However, they also come up to the top of the tank for air. 

While their tank will need a heater, it won’t need a filter since this species takes its janitorial career seriously. 

You’ll need a solid container to move these guys because their spines can get tangled in nets and can puncture your skin. Their spines are mildly venomous, but the feeling is luckily like an ant bite.

  • Maximum size: 1.1 inch
  • Temperature: 72°-77°F

10. Scarlet Badis

Scarlet badis are beautiful scarlet-banded fish that many hobbyists keep for their looks. However, they’re sensitive to water conditions, so you’ll need to take special care.

Scarlet badis are more shyster than baddy with most species. If their tank mates aren’t calm, slow, and peaceful, they won’t leave their hiding places and feed. However, they do consider snails and shrimp as food.

They’re best in a dedicated scarlet badis tank. Male and female pairs are ideal, or you can keep all females with just one male. Males can be aggressive toward one another, so keeping only one male per 10 gallons allows them to stake their territory.

  • Maximum size: 0.79 inches
  • Temperature: 72°79°F

11. Snails

Aquatic snails of all sorts are great for helping keep your tank clean. They find algae, dead plants, and dead fish to be tasty delicacies, so you’ll want one around. 

Some fish like to dine on snails, so be sure to determine your tank’s dietary preferences before adding one to your tank if you’re not adding them as treats. 

Keep in mind that you still need to count the size of your snail for the sake of your tank’s bioload. Plus, you’ll want no more than 1-2 snails per five gallons.

  • Maximum size: 1-5 inches (depending on species)
  • Temperature: 65°-82°F

12. Shrimp

Shrimp can make exciting additions to a nano tank. They come in various intriguing colors, and their movements are mesmerizing. The most popular is the red cherry shrimp since they’re hardy and easy for beginners.

You’ll want to make sure shrimp isn’t a dietary delight for other tankmates before adding them in. 

Shrimp-only tanks can be enjoyable as well, whether you’re keeping them as a feeder tank or for beauty. However, it’s best to keep just one color per tank because hybrids will usually end up brown or clear.

  • Maximum size: 1.5 inches (male) to 2 inches (female)
  • Temperature: 65°-84°F

Types of Fish That Should Not Be Kept in a Nano Tank

There are several fish that don’t belong in a nano tank:


If your memory of goldfish mainly involves goldfish funerals, there’s a reason. Goldfish create a lot of biowastes quickly. Thus, they often die from dirty water. Goldfish also grow 6-24 inches long, so small tanks don’t give them enough room to swim.


Sparkling, croaking, honey, and dwarf gouramis are small enough nano tanks. Kissing gouramis need at least a 55-gallon tank, and giant gouramis need a 250-gallon tank. Others are small enough to thrive in tanks 30 gallons or larger.


Most cichlids need a large tank because of their adult size and aggressive behavior. While some African cichlids do okay in 30-gallon tanks, most South American and African cichlids need at least a 55-gallon tank. 

Exceptions are dwarf South American cichlids, which can happily live in 10- to 20-gallon tanks. 

What Kind of Fish Can You Keep in a Nano Tank?

The best fish for nano tanks are small, hardy, and cold water fish.

Small Fish

There are two main reasons it’s best to keep small fish in a nano tank: fish quantity and quality of life. 

Since the size of an aquarium limits the number of fish you can have, you can fit more small fish into a nano tank than large fish. Therefore, the smaller the fish, the more you can fit in your tank. 

Additionally, if you keep large fish in a small tank, you aren’t providing them with a good quality of life. If your fish are nearly as long as the tank, they won’t be able to swim very far and will not live as long as they would in a larger tank.

Hardy Fish

Remember all those sitcom episodes with fish funeral scenes? Those are mainly the result of having finicky fish in a fishbowl (the original nano tank). 

When you have a nano tank, you can overwhelm the bioload quickly (the nitrogen-processing demand of your filters). Overwhelming the bioload is especially likely if you’re not changing the water often enough and have a lot of fish. 

Be honest about how often you will change the water before determining your fish types and aquarium size. For example, most hobbyists don’t recommend a nano tank under 20 gallons for beginners because it’s so easy to upset the bioload.

Cold Water Fish

If your nano tank is the type that is too small for a heater, you’ll want to consider cold-water fish instead of fish that are accustomed to water that’s room temperature or above.

If you keep tropical fish like bettas in cold water, they become less active and often die. Keeping tropical fish in cold water tanks can also slow down their immune system, making them more susceptible to disease.

How Many Fish Should You Keep in a Nano Tank

When determining how many fish you can keep in your nano tank, keep in mind that you can keep one inch (2.54 centimeters) of fish per one gallon (3.8 liters) of water. 

When determining how many fish to put in your tank, remember that fish grow and research their maximum adult size. 

Keeping Fish in a Nano Tank – What You Need to Know

Keeping fish requires more than just a tank, fish, and food. You will need equipment to take care of your fish and a regular schedule for changing water. 

Equipment You Need

  • Heater: for fish needing water room temperature or above
  • Filter: for larger tanks with less-frequent water changes
  • Tank vacuum: for partial tank changes
  • Small bucket: to hold water for water changes unless your vacuum attaches to your sink
  • Net and holding container: for water changes
  • Nitrite and ammonia testing kits: to make sure the water stays safe
  • pH testing kit: to keep the water the correct pH for fish with special pH needs
  • Water conditioner: to neutralize chlorinated water
  • Fish food: choose a type appropriate for your fish

Water Change Frequency

How often should you change the water in a nano tank? 

  • ½ gallon: 100% water change, twice per week
  • 1 gallon: 100% water change, once per week
  • 2-3 gallons: 50% water change, once per week
  • 5-10 gallons: 25% water change, once per week
  • 15-30 gallons: 10% to 15% water change, once per week

Not rinsing rocks, decorations, or the tank during water changes will help maintain healthy bacteria levels.

Tip: Don’t forget to add a water conditioner and ensure that the water you reintroduce into the tank is approximately the same temperature to prevent killing your fish.

Beautiful Nano Tank Ideas and Stocking Options

Here are some of the best fish for nano tanks with ideas for gorgeous plantings.

20-gallon puffer tank:

  • Three pea pufferfish
  • Java moss
  • Java fern
  • Sunset hygro

20-gallon betta sorority tank:

  • Eight female bettas
  • Vallisneria
  • Java moss
  • Java fern

20-gallon combo one (all coldwater)

  • Eight ember tetras
  • Two zebra danios
  • Two white cloud minnows
  • One nerite snail
  • Two Amano shrimp
  • Java fern
  • Java moss
  • Anacharis

20-gallon combo two:

  • Three zebra danios
  • Eight ember tetras
  • Four pygmy corydoras
  • One mystery snail
  • Java moss
  • Java fern
  • Anacharis
  • Hornwort

10-gallon combo one:

  • One cherry shrimp
  • One mystery snail
  • Eight ember tetras
  • Java moss
  • Java fern
  • Vallisneria 

10-gallon combo two: 

  • One sparkling gourami
  • Four pygmy corydoras
  • Six scarlet badis
  • Hornwort
  • Rotala rotundifolia
  • Java moss

What Aquarium Plants Can You Add to a Nano Tank?

Here are a few live plants that would work well in a nano tank:

  • Sagittaria
  • Vallisneria
  • Java moss
  • Anubias
  • Java fern
  • Green hygrophila
  • Moneywort
  • Waterwheel plant
  • Sunset hygro
  • Rotala indica
  • Rotala rotundifolia
  • Hornwort

Our Recommendation for the Best Fish to Keep in a Nano Tank?

Perhaps, the easiest fish to take care of in a bowl or small fish tank is White Cloud Minnows. It’s small (grows up to a maximum of 1.5 inches) and hardier than most small schooling fish, and can withstand most of the mistakes by novice fish caretakers. The only exception is copper medication.

Our Recommendation for a Great Nano Fish Tank


Here are answers to a few more questions you might have about your nano tank.

What Saltwater Fish Can Live in a Nano Tank?

Here is a shortlist of saltwater fish you can keep in your nano reef aquarium.
  • Clownfish (Amphiprioninae) 
  • Clingfish (Gobiesocidae) 
  • Cardinalfish (Pterapogon kauderni) 
  • Basslet Fish (Grammatidae) 
  • Fire Fish (Nemateleotris magnifica) 
  • Goby (Gobiidae) 
  • Yellowhead Jawfish (Opistognathus aurifrons)

What Is Considered a Nano Tank?

A Nano tank is typically anything smaller than 5 gallons. However, for the purpose of this article, we focused on anything smaller than 20 gallons

Before you leave, check out our list of the most popular aquarium fish for more great ideas you can use in your next aquarium.

Jack Dempsey
Follow Me