Asian stone catfish

20 Perfect Freshwater Nano Fish For Your Tank

Tiny fish and tiny aquariums are cute and really interesting to set up. Nothing is cooler than watching a functioning tiny ecosystem right on top of your work desk or bedroom drawer!  This is now possible thanks to the rise of nano tanks. 

You may also like:

What qualifies as a Nano tank?

Nano tanks are basically smaller tank set ups, normally 20 gallons or less, which are designed towards coming up with a small eco-system for tiny fish. They are nowadays preferred because they are can nicely fit in all apartments or houses and are a smaller investment in comparison to larger tanks.

They have gained popularity over the past few years and most people even include live plants and decorations in their tanks. Despite their small size, they still offer numerous decoration and configuration options. You could create a tiny garden, submerged jungle, or even a miniature mountain range; the choices are endless! 

What’s more, numerous vibrant fish species can live in such tanks. However, note that it is important that tiny fish are housed with other tiny fish. This is recommended to avoid unnecessary competition for food, for instance when housed with larger species. Remember that your tank is only 20 gallons big at maximum.

But just because these tanks are small does necessarily mean less work. In fact, the smaller your tank the more the maintenance needed, and the more important it is to ensure that your water quality is always on point. In addition, most tiny fish require special care.

That said, below is a list of 20 nano fish species that you could consider stocking in your freshwater aquarium.  All of the fish in this list can do well in tanks with a capacity of 5 to 20 gallons of water.

Let’s get to it!

1. Asian stone catfish

Asian stone catfish 

This is one of the smallest and cutest catfish species that you could find for your aquarium. With a maximum length of just over an inch, this charming, whiskered catfish species will definitely be a unique and special addition to your aquarium. You should, however, not anticipate a lot of action from this tiny creature as it is really inactive and often stays in one place.

The Asian stone catfish is quite peaceful and it co-exists well with almost every nano fish featured in this list. You can house it alone but it does better when in small groups. This fish does best in a tank with a soft substrate, sufficient hiding place, almond leaves or driftwood. Good water quality is essential for the survival of these small creatures and it must be kept clean, stable, and properly oxygenated at all times. 

This catfish species is nocturnal and so feeding should be done when it is dark. They can feed on dried pellets, bloodworms, daphnia, and brine shrimp.

2. Scarlet Badis

With regard to looks and size, these tiny creatures are just the perfect pet for your nano aquarium, requiring a minimum of just 5 to 10 gallons of water to do well. Do not, however, let their tiny size fool you. These fish species can at times get aggressive, particularly towards fellow males.

The females tend to be approximately 0.7 cm smaller than the males, and one simple way of distinguishing the males from females is the unique ventral fin that they have. 

The most important thing to remember when dealing with this particular fish species is that they are natural predators. Aquariums featuring different objects such as decorations and live plants are recommended to prevent tensions from rising. This is because these objects cut off all clear lines of sight that could be pathways towards aggression.

When it comes to their diet, they should be fed on a mixture of dried foods and flakes.

3. Scarlet Gem

The scarlet gem is a gorgeous tiny fish with a body shape that strikingly resembles that of a dwarf cichlid, though they are not related at all.  They are very timid and quite peaceful when housed with fish of similar temperament and size. 

Because of their timid and shy nature, a lot of care should be exercised to make sure that they are well fed. They do not feed on dried foods and should thus be fed on different kinds of frozen and live foods such as daphnia, banana worms, and shrimp. Note that these fish tend to become obese and develop diseases when fed on tubifex worms and bloodworms (these two should be excluded from their diet).

4. Pygmy Cory Cats

Pygmy Cory Cats

Originating from South America, pygmy cory cats are one of the most adorable aqua pets that you could stock in your freshwater aquarium. The pygmy cory maxes out at approximately an inch in length and should be kept in groups of 3 to 6 individuals.

Being omnivorous creatures, pygmy cory cats can be fed on sinking foods and frozen foods like bloodworms and tubifex worms. You should, however, not expect them to survive on food leftovers from their fellow tank mates. They are also not aquarium cleaners.

5. Licorice Gouramis

Licorice Gouramis

The licorice gouramis are one of the tiniest of the gourami species, maxing out at one and a half inches in length. This gourami species is quite peaceful and can co-exist in pairs or groups without any troubles. Gouramis are part of the labyrinth fishes and they have a special organ known as a labyrinth that enables them to obtain draw air from the surface of the water.

Licorice gouramis do well in slow-moving to stationary waters such as pools, flooded fields, and swamps. Such habitats are very acidic, have limited oxygen supply, and are very rich in nutrients. Maintaining such soft yet acidic water in your aquarium can be achieved with the help of almond leaves, adding driftwood, as well as reverse osmosis.

When it comes to feeding, these tiny fish do best when fed on mixed frozen and live foods such as bloodworms, tubifex worms, daphnia, and brine shrimp.

6. Pea Puffer

Most pufferfish species are known to survive in salty water but this particular species is different. The pea puffer is the tiniest pufferfish species and can be housed in an aquarium with a water capacity of as little as 5 gallons. They max out at just above one inch in length and should only be housed with one another or tiny catfish and tiny gobies like the bumblebee. 

Despite their small size, these fish tend to be very aggressive and aren’t suitable tank mates for other tiny fish. They cannot be housed with larger fish species too. Also, pea puffers are at times aggressive towards one another and thus care should be observed to maintain a ratio of 1:2 males to females. Also, a five-gallon aquarium should hold no more than three puffers.

Because of their curiosity, these fish do well in a fish tank that has lots of hiding places and is heavily planted. Adding pea puffers to your aquarium is always a delight; they are quite inquisitive and often swim towards the glass of your tank when they see you approaching. And similar to other pufferfish, pea puffers inflate their stomachs with air or water when threatened, doubling or tripling its size.

Being carnivorous, they mainly feed on tiny crustaceans, worms, and mollusks when out in the wild. Their diet should comprise of frozen krill, bloodworms, and brine shrimp. 

7. Salt and Pepper Catfish

Salt and Pepper Catfish

Tracing its origin back in South America, this catfish species can grow to a maximum length of one and a half inches. And given that they are native to tropical surroundings, they are mostly found in wetlands. They, however, prefer shallow waterways, which are quite dangerous as they often dry up. Their tank surroundings should be a little bit dense with leaves and plants, molded after those tropical conditions that they are used to.

These fish are tiny, hardy fish are quite interesting to watch. When housed in an aquarium, they often swim up to the water surface for a few gulps of air. And even though it is a normal phenomenon for this particular species, in case you observe other fish in your tank doing the same, it might be a sign of a drop in your tank’s oxygen levels.

Salt and pepper catfish do well in small groups and feed on different kinds of pellets and flakes. They particularly enjoy eating brine shrimp. They are known to be peaceful fish and are a great option for beginner aquarists.

8. Otocinclus Catfish

When it comes to algae eaters, this is one of the best fish species to add to your aquarium! They do an incredible job of keeping your tank’s glass, plants, and décor free of algae. These tiny mowers have a huge appetite and will thus need some sort of algae supplement in form of wafers, pellets or flakes if the algae habiting your tank is not enough.

They are one of the most peaceful nano fish and can be housed with several other fish species.

9. Sparkling Gouramis

If beauty is what you are looking for in your fish, then sparkling gouramis is what to settle for. Their green, blue, and red sparkles will make them beautifully stand out in your tank. They are indeed a beauty to behold!

These fish are shaped like tiny arrowheads and max out at about one and a half inches in length. They are a very peaceful species and their tank should have a capacity of at least 10 gallons or more. 

Apart from being a poor choice for companionship, sparkling gouramis are known to be tolerant to different water conditions and environments. This is partially thanks to their labyrinth organ, which allows them to have a substitute breathing technique, something that most other fish do not have. 

These fish are not picky eaters; they enjoy all sorts of foods but a diet made up of live and frozen foods like brine shrimp and bloodworms is ideal. The only challenge in keeping this fish is getting a suitable tank mate for them.

10. Hara Jerdoni

This is a tiny freshwater fish native to India. It is one of the smallest catfish species out there and it makes for a perfect pet for nano tanks. This bottom-dwelling and whiskered fish are cute, hardy, and very inactive. They are comfortable in tiny tanks and don’t seem desperate for any extra room to move about.

They often stay in one location for the most part of the day thus making them great companions for other fish. Their unsocial nature, however, does not mean that they do not need any care.

Setting up the perfect habitat is the most challenging part when keeping Hara Jerdoni as pets. These fish require aquariums with some sort of cover, beneath which they can relax for hours. Simply put, their tanks should have plenty of hiding spaces. In addition, these fish need aquariums with above-average levels of oxygen to thrive.

Even though they can be housed alone, it is recommended to keep them in groups for company. They are nocturnal creatures and when it comes to feeding time, they prefer froze, dried, or live food such as worms and shrimp.

11. Amanda Tetra

Also called Ember tetras, these fish resemble small floating flames when housed in an aquarium with a darker substrate. They are active, quite peaceful and d best when in groups of five or more.

Their diet should include tiny dried foods like small flakes and pellets. They can, however, be supplemented with tubifex worms, brine shrimp, as well as planktonic foods.

12. Green Neon Tetra

Green Neon Tetras are a popular choice among most hobbyists. Even though they are just a bit less colorful than other Tetras, they are still gorgeous to look at and make up for this by being perfectly sized for nano tanks.

Apart from being obviously gorgeous, green neon tetras as peaceful fish and happily co-exist with fellow tank mates. They prefer consuming a mixed diet composed of a variety of pellets and live foods and are capable of growing to a maximum length of just one and a half inches.

Before stocking your tank with the green neon tetra, it is advisable to first research the Neon disease that attacks these fish from the inside out. A common symptom of the disease is white patches on the fish’s skin.

13. Bumblebee Goby

This is the only nano fish in this list that’s brackish. Some hobbyists, in fact, insist that these fish do better in brackish surroundings, which is actually far from the truth. Bumblebee gobbies originate from different environments including estuaries, freshwater habitats, and swamps whose waters could be very acidic as a result of the high tannin concentrations. Thus, bumblebee gobbies are adaptive to both freshwater and brackish environments and can do well in either. All they need is a healthy diet.

Their diet should be high in protein. They should be fed on live or frozen foods such as brine shrimp, daphnia, bloodworms, or tubifex worms.  

They somewhat peaceful but could be quite aggressive towards each other if a lot of them are housed in a tiny tank. A five-gallon tank should house one bumblebee goby.

14. Micro Cyprinids

Micro Cyprinids

These fish are very tiny and there are numerous varieties of them. They are very timid and shy and will only exhibit some activity when provided with plenty of places to hide. They do best when stocked in groups of 5 to 6 or even more.

They are omnivorous and will feed on tiny pelleted foods, flakes, and frozen snacks such as daphnia, bloodworms, brine shrimp, and tubifex.

15. Annual Bluefin Killifish

If you want a pop of color then this is the fish to include in your tank! The annual bluefin killifish is stunning and will make an incredible centerpiece for your tank. Native to swamps and pools that experience wet and dry seasons, their natural habitats get desiccated resulting in the death of all adult killifish. But just before the dry season, killifish lay their eggs and once the rainy season begins, the eggs hatch and the life cycle starts all over again.

They are carnivores and can thus be fed on frozen bloodworms, tubifex worms, and brine shrimp.

16. Least Killifish

Least Killifish

This Killifish species is native to Southeastern America and is very closely related to Mollies and Guppies. They breed quite often in home tanks and instead of laying eggs (like most Killifish) they actually give birth to live little ones.

Least Killifish grow to approximately 1.5 inches in length and can do well in a tank with a capacity of as little as 3 gallons. They are quite accepting of a wide range of water conditions and are capable of thriving in different environments.

Their diet should comprise of meaty treats as they are carnivorous creatures. They should be fed on frozen bloodworms, tubifex worms, and brine shrimp.

17. Norman’s Lampeye Killifish

Norman’s Lampeye Killifish

If you are searching for a freshwater fish species that really does well in nano tanks then look no further than the Norman’s Lampeye Killifish. They are tiny freshwater fish popular for their resilient and peaceful nature. These fish cope well in different water conditions and environments, making them a nice option for amateur aquarists.

Lampeyes should be housed in groups of 3 to 5 fish, and given that they remain pretty small in size (with a maximum length of about 1.5 inches), a 5 to 10-gallon tank can easily house one group. They do even better in tanks with lots of live plants, which makes them the best option for those wanting to set up a planted aquarium.

18. Betta Fish

Betta fish are among the most common fish in fishkeeping and they are loved for their hardy nature and striking colors. They can survive in tiny aquariums as they are somewhat flexible with regard to water conditions thus making them a nice choice for beginners.

400;”>Bettas are peaceful fish and should be housed in tanks with a capacity of at least five gallons that’s well-equipped with a filter and heater. Note that this fish species should not be kept in tiny bowls or cups.

19. Celestial Pearl Danios

Danios come in different sizes and shapes and the celestial pearl danio is one of the smallest in this group. This tiny freshwater creature is extremely colorful and quite interesting to watch in an aquarium, which is precisely why it is a favorite amidst several hobbyists.

These fish should not be housed alone but instead in groups of 4 to 6 fish. A tank with a capacity of 5 gallons can house one group though a 10-gallon is recommended where possible. If you, however, choose to go for a smaller tank, just ensure that water changes are done regularly.

Celestial pearl danios are not picky when it comes to food. Being omnivores, their diet should comprise of a mixture of both meat- and plant-based feeds such as freeze-dried bloodworms, brine shrimp, algae wafers, and flake foods. 

20. Endlers Livebearers

This is a tiny freshwater fish popular for its strikingly bright and psychedelic patterns. Similar to other livebearers, Endlers breed regularly. This means that you should be well prepared for some young ones if you intend to include this particular species in your aquarium.

On top of their breeding tendencies and amazing colors, Endlers are also very easy to rear. They are tolerant of different water conditions and this makes them a perfect choice for low maintenance aquariums and beginners. They are also known to be very peaceful.

Similar to most other fish species on this list, Endler’s livebearers are omnivores and a simple diet of flake food accompanied by some meaty snack will do just fine.

Factors to Consider when setting up a Nano Tank

When setting up your nano tank, there are certain factors that you need to consider, all based on the species of fish that you have settled on. They include:

The nitrogen cycle

This is the most important consideration! Once you’ve stocked your aquarium, there’s no doubt that your fish will poop and pee. After a while, these wastes begin to disintegrate resulting in the production of ammonia, which is extremely toxic for your aqua pets. And as more and more waste is produced, the levels of ammonia in your tank water increase as well.

Fortunately, numerous beneficial bacteria help to convert the released ammonia into nitrites and then nitrates, and it is this change that is known as the nitrogen cycle. These bacteria, however, do not just show up immediately your tank is set up; a bit of time is required to allow for the buildup of these bacteria. 

Tank size

This is another important consideration. The size of your tank will determine both the species and the number of fish you can keep, as well as the type of plants that can be planted in your aquarium. That said, it is not advisable to use a tank that has a capacity of fewer than 5 gallons. Going for an extremely small tank means that you will have to conduct more water changes, even when only a single fish is housed. 

Bigger is normally better! In fact, experts recommend using 20-gallon fish tanks for nano fish. The greater the water volume, the more dilute the waste. This means that you could go longer between water changes.

Plants and decorations

The type of plants you plant and decorations that you intend to include in your tank should be determined by the fish species you want to keep. There are those species that prefer densely planted aquariums whereas others might want open swimming spaces.


Getting the right filter for your tank is very important. Get a filter that has a GPH (gallon per hour) of at least four times your tank’s capacity. For instance, you would want a filter with a GPH of at least 60 for a 15-gallon tank.

You also need to conduct some research on the fish species you want to keep in order to know the kind of current they prefer. Weak swimmers, such as bettas would do well with filters that produce a gentle flow.


There lots of substrate choices to use for your tank. Some substrates can alter the tank’s water chemistry and so you need to find out more about your chosen substrate before adding it to your tank. Examples of substrates that you can use include gravel, sand, and soil. 


Whether or not you will need to include a heater in your tank depends on the fish you will house. Most nano fish are native to tropical regions and so will definitely need a heater.

Final words

There are lots of beautiful nano fish available on the market today, which makes it easy to see exactly why nano tanks have become the trend. Nano tanks are not stunning, but they also fit into lots of budgets as well as living situations.

Just remember to set up your tank based on the fish species you intend to keep.