small fishes for nano tanks

15 Small Freshwater Fishes for Nano Tanks & Aquariums

Freshwater fishes are those that live in freshwater bodies such as rivers and lakes. They mostly suit water with a salinity of less than 1.05%. However, many other environmental factors make a difference between freshwater conditions and marine surroundings.

Small freshwater fishes are highly suitable for nano tanks. Such fishes can live comfortably in these small setups. Usually, a nano tank carries 20 gallons or below this amount. It is like a tiny ecosystem for fishes, which is easy to carry and consumes less space.

So, here in this article, we will provide a full-fledged guide of the best and most suitable freshwater fishes that you can have for your nano tank. With a brief description of each fish, you can make a proper decision for the sake of both you and your fishes’ comfort. This guide will also let you know the essentials to keep in mind as you set up a nano fish tank. So, now let’s begin.


15 Small Freshwater Fishes for Nano Tanks & Aquariums

1. Harlequin Rasbora

This tiny fish is pretty fun to watch. Harlequin Rasbora is native to the blackwaters in Southeast Asia. Also, this breed is quite popular in the aquarist community. You can also call them shoaling fish, which means that they prefer to travel and live in large groups. Because of this reason, there exists a thumb rule that at least two Harlequin Rasboras should be kept together in each gallon of water.

It is wise if you keep them in a group of at least 6 to make them feel safe and confident in their new home. Harlequin is the name given due to its shinning and sparkling appearance. The body has a pinkish-orange hue. The lower half of the body has bold features. It has triangle-shaped spots of black color.

Harlequin Rasboras are pretty easy to take care of; therefore, you need not worry. They are omnivorous by nature; hence they mostly feed on flake foods, dried and frozen bloodworms, and tubifex. Also, being peaceful, some suitable mates of Harlequin Rasbora are Rummy Nose Tetra, Danios, and Dwarf Gouramis.

Harlequin requires water at a temperature of about 74°F, and the pH level for the water should be somewhere around 6.5. Each of these fish is of the size of 2-inches. They can be kept in a nano tank of a minimum capacity of 10 gallons.


2. Neon Tetra

It is one of the most common and famous fish among the aquarist community. Neon Tetras can live in both large as well as nano tanks. Its name is given because of its coloration. The body of this fish is covered with bold and vibrant stripes, in blue and red color. They are omnivores by nature. They can be fed either flake food or micro pellets.

They also belong to the schooling category of fishes, and it is better to have them in groups. In this way, they will feel comfortable and familiar with the place. Having a group of Neon Tetra will let you enjoy their chorus movement and swath in the water. The colors shine bright and bring lively aura to the tank.

They are native to the Amazon River, where they are found in groups of thousand such fishes. They have small and thin fins with an overall size of 1.2-inches. You can keep them in a nano tank, which is of a minimum capacity of 10 gallons. Neon Tetra requires a pH level of water at around 6.0-7.0. The temperature for their stay has to be 72-76°F.

They have a peaceful temperament. So, if you want tank mates for Neon Tetra, you can choose fishes such as Guppies, Mollies, Loaches, and Cardinal Tetras.


3. Betta Fish

This fish is known for its aggressive behaviour. But otherwise, they are gorgeous. They will often show you their beautiful colors and grills when you look at them consistently. You can have Betta Fish in different color variations. All of their varieties are vividly beautiful and eye-catchy.

The aquarist stores usually sell male Betta Fish. Their fins are long and give a view of the ever floating image in the water. In comparison to the male Betta Fish, females have less vibrant colors and not much variation. They also lack the silky tale as that of the male Betta Fishes.

They do not go along well in a group; so you should prefer keeping a single Betta Fish in a tank with some other species of fish for the company. The best tank mates for Betta fish can be Cory Catfish, Ghost Shrimp, Guppies, and Neon and ember tetras.

They are of the size 2.25-inches each. You can keep them in a tank of a minimum quantity of 5 gallons. They usually require a pH level ranging between 6.5-7.5. The optimum water temperature required for their survival is 78-80°F. Betta Fishes are predatory by nature. So, their diet includes frozen or dried bloodworms.


4. Cardinal Tetra

Another small freshwater fish is Cardinal Tetra. It is a schooling or shoaling fish breed. Try to keep them in a group of 6 or more. Now, these fishes are quite similar to the appearance of the Neon Tetra fishes. But if you want to see the difference, you can see that the Cardinal Tetras have some very subtle differences, which tell the character of the breed.

The first and foremost difference between a Neon Tetra and Cardinal Tetra is that the latter fish gets an inch bigger from the former one, over time. Unlike Neon Tetra fishes, which have a blue head and red tail, Cardinal Tetras don’t have such features.

Cardinal Tetras have a long and thin body shape. They have blue and red bold stripes on their body, similar to the Neon Tetras. The thing is that the stripes of Cardinal Tetra extend throughout their whole body, but the same is not the case with the Neon Tetras.

They are peaceful by nature, and therefore, can stay in groups. You can have them in your nano tank along with some tall plants,as they love to dash in and out of those plants in groups. Most suited tank mates of Cardinal Tetra are Neon Tetras, Zebra Danios, Mollies, and Guppies.

The size of the Cardinal Tetras is about 2-inches. The minimum capacity of their nano tank can be 15 gallons. It is easy to care for Cardinal Tetra, and you do not have to worry much, as it requires a water temperature of only 72-76°F. The pH level of the water should be around 6.0-7.0. Also, they are omnivorous; therefore, you can feed them with flake food, small pellets, and live or frozen daphnia.


5. Chili Rasbora

The aquarium or fish tank looks beautiful when you can have a good number of fishes in it. Chili Rasbora is a breed that lives in a group. This shoal category of fish is preferable to keep in groups of 6 or more. You can also call them mosquito rasboras.

Chilli Rasbora is a native fish to Borneo. It is quite a famous pick when it comes to nano tanks. This freshwater fish is exceptionally red, which makes it eye-catchy. On this red body, Chili Rasbora has decent black stripes that are bold at the upper part of the body and starts to fade into thin lines till the end of their tails.

These fishes are always on the move, and amazingly energetic. You would hardly see them settled. The usual size of Chili Rasbora is 0.75-inches, which is quite tiny. They require nano tanks of a minimum capacity of 5 gallons.

Also, they live in a water temperature of 20-25°C, and the pH level of the tank water must be about 5.0-7.0. Chili Rasbora is carnivores, and therefore they can be given crushed flakes or baby brine shrimps to eat. Do you want to have tank mates for Chili Rasboras? You can go with Minnows, Tetras as well as small Catfishes.


6. Fancy Guppies

It is another schooling fish that likes to live and travel in water in groups. It is suggested to keep Fancy Guppies in a group that has either all males or one male and the rest females. Restrain from keeping a female with many males as she can be dominated.

The reason behind keeping the only male group is that this breed reproduces extensively. But if you want babies of Fancy Guppies, then you are welcome to get the females along.

The best thing about Fancy Guppies is that they come in a huge number of color variety. Their body shape is long and slim. The males have large, vibrant, and colorful tails, whereas the females are deprived of it. These tiny fishes have a subdued silver color.

With a size of 2-inches, these Fancy Guppies can stay in a tank of a minimum quantity of 5 gallons. Although this breed is mostly peaceful, the males sometimes tend to dominate and harass their female counterparts. For having suitable tank mates for Fancy Guppies, you can go with Cory Catfishes, Harlequin Rasboras and Cardinal Tetras.

The approximate water temperature for their survival is 21-27°C, and the pH level of water should be 7.0-8.0. Fancy Guppies are omnivorous and can be fed micro pellets and Mysis shrimp.


7. Endler’s Livebearers

Endler’s Livebearers can be kept in groups. It is prescribed to have a group of either all males or one male and three to four females. This breed is closely related to Fancy Guppies, as they have almost similar body structures. But, the color of the male Endler’s Livebearers is very bright and vibrant.

It seems like you have given a neon marker to a child, and he has poured all his ambitions on the fish. The males are a thing to watch. And it is not just about the neon color, Endler’s Livebearers come in many color variations.

Now, why do we suggest you buy a group of males in the first choice? There is a reason behind it. The Endler’s Livebearers reproduce like crazy. You cannot bear it or provide proper care to the newborns.

Endler’s Livebearers sizes 1-1.8inches, and they can live in a nano tank, which sizes 5 gallons. They are peaceful by nature. So, for tank mates of Endler’s Livebearers, you can choose other friendly fishes such as Tetras, Honey Gouramis, and Glass fishes.

The temperature of their tank water has to be somewhere between 75-80°F. Their diet involves micro pellets, flake food, and frozen bloodworm as Endler’s Livebearers are omnivores.


8. Zebra Danios

If you are having the first experience with small freshwater fishes, then Zebra Danios is the best one to start from. It is a schooling fish, which should be kept in a group of five or more. The name Zebra Danios is given to denote the zebra-like print present on the body of the fish. It has black and white stripes like a zebra, but the difference is that it has the lines horizontally on the body.

Zebra Danios have a long slim body, and their fins are round in shape. The color of their bodies is silver from head to tail. On that silver, you can see the strips of blue metallic color. These strips run from their nose to the tail.

Although they are fine to live in nano tanks, Zebra Danios are quite active in their motion. Also, you are suggested to have green plants in your nano tank as they love to swim inside-out of them. However, some suggest having them live in larger aquariums for their free motion.

They size about 2.5-inches and can live in a nano tank of 15-gallon capacity. They are calm and easy-going by nature. You can set the water temperature at 18-25°C for them. Also, they require a pH level of 6.5-7.5.

You can feed them with frozen daphnia, bloodworms, or flake food because they are omnivores. So, now, if you are thinking of having tank mates for your Zebra Danio, then you can have Tetras, Guppies, Rasboras, Loaches, and even Catfishes.


9. Bluefin Notho

These fishes do not live in a shoal. They are better when there are only one male and several females. These are one type of Killifish. That’s one of the reasons why male Bluefin Notho is not preferable to keep together in groups.

They are usually caught from wilds. Bluefin Notho is found living in tiny water bodies, as they do not require much of a larger water body. That is why they are apt for nano tanks. Living in small water bodies, Bluefin Notho dies eventually as the water gets dried up every year. The adults die, leaving the eggs behind, and that is why Bluefin Notho lives for only 1-2 years.

They have slim bodies and are long from head to tail. They are mostly known for their bright red coloration. The design of these fishes is fantastic. Their body has metallic blue spots, whereas their fins and tail have stripes of the same blue metallic color.

Bluefin Notho sizes about 2.4-inches and can stay in a tank of 10-15 gallons capacity. The temperament of these fishes is semi-aggressive, and the heat of aggression can strike up between the males. So, they must be kept with companions of larger sizes.

The water temperature of their tank needs to be 20-24°C, and the pH level is stated to be 6.0-7.0. Bluefin Notho is predators in nature; therefore, they are required to be fed frozen and live food such as Cyclops, baby brine shrimps, and daphnia.


10. White Cloud Mountain Minnow

White Cloud Mountain Minnow is a breed that lives and travels in school. It can be kept in a group of a minimum of 6 or more fishes. A group of fishes staysmore comfortable and healthier together in a new environment. Also, a shoal of White Cloud Mountain Minnows will make your tank livelier.

White Cloud Mountain Minnow has a long and slim body shape. They have two prominent colors. One is a bright golden, and the other is silvery blue. Both of these colors hold their own elegance. However, the color of their fins and tail is red in both of them.

White Cloud Mountain Minnow are usually bred to feed the larger fishes and their species. Therefore you can have only the males or a few females if you want. One important thing to keep in mind is that White Cloud Mountain Minnow does not require a heater for their water tanks.

The size of these fishes is 2-inches, and they need a tank having a capacity of about 10 gallons. These are easy to care for and peaceful by nature. White Cloud Mountain Minnow requires a water temperature of about 7-21°C. The water should have a pH level of 6.0-8.0.

As the White Cloud Mountain Minnows are omnivorous, their diet contains baby brine shrimps, bloodworms, and even flake food. White Cloud Mountain Minnow is best suited with tank mates such as Tetras, Barbs, Platies, Loaches, and Discuses.


11. Oto Cats

These cats are super easy to have and take care of. Oto Cats are another example of a schooling breed of fishes. They like to travel in groups. You should have at least five or more of them. Oto Cats are also known as dwarf catfishes or dwarf fishes. It is like having kids in an aquarium who run naughtily from one side to the other.

They usually feed on algae; therefore, you don’t need to arrange much of any special food for them. It is fantastic to have Oto Cats because they keep your tank clean by eating all the algae and unwanted debris. They are also called ascommunity tank cleanup crew. However, Oto Cats are natural herbivores. And therefore, they can eat algae wafer and blanched vegetables such as broccoli or zucchini.

These fishes are peaceful and calm by nature. Hence, they can be kept with tank companions, including Cory Catfishes, Shrimps, and water Snails.

Oto Cats grow to a size of about 2-inches. They require a minimum size tank of 10 gallons of capacity. The suitable degrees of water temperature would range from 22-28°C. Also, the water should have a pH level of 6.0-7.5.


12. Pygmy Corydoras

Pygmy Corydoras are supposed to stay in groups. These are highly delicate fishes. If not kept in a group, they might become insecure and not feel comfortable. Therefore, you must keep together at least six of them.

Pygmy Corydoras are also called as miniature catfishes. Unlike other fishes with slim body types, Pygmy Corydoras have humped back. The foreheads of these fishes are slightly sloped towards the hump at the direction of their dorsal fins. Because of this reason, they are keen bottom dwellers.

These fishes are also perfect cleaner for any water tank or aquarium. The character of the Pygmy Corydoras is quite funny. They act like toddlers who are left open in candy stores. Their movement is very active and settles quite less.

Pygmy Corydoras are subtle and calm by nature. So, the most suited tank mates of Pygmy Corydoras are Neon Tetras, Dwarf Gourami, and Mollies. Also, the diet of Pygmy Corydoras includes pellets, wafers, and frozen bloodworms as they are omnivores. Gel foods are also suitable for them.

Pygmy Corydoras are pretty small in size, about 1.2-inches. They should be kept in a water tank with a capacity of about 10 gallons. They live in a water temperature of about 22-26°C. The tank water that they live in should have a pH level of about 6.4-7.4.


13. Sparkling Gourami

These fishes are one of a kind that does not belong to the schooling category since they do not like to swim in groups. You can still have a group of them as they are very peaceful by nature. Unlike other fishes with a long body and round fins, Sparkling Gourami has a real compressed body. Its deep chest slants towards the tail giving it a flat shape.

Sparkling Gourami mostly comes in two primary colors, which are grey and beige. On the colored bodies, they have either metallic red or metallic blue spots or speckles. But the fins are different. They are generally transparent and have more amounts of metallic flecks on them, mostly arranged in rows. The most interesting thing about their appearance is their eyes, which look wide and metallic.

These tiny Sparkling Gouramis size up to 1.5-inches only. They can live in a tank that has a minimum capacity of up to 10 gallons. Besides, they also have an easy-going nature. Their surviving temperature should be 24-27°C with water, having a pH level of about 6.0-7.0.

Sparkling Gouramis are omnivores by nature. They grow and live better when given animal protein with algae. You can provide them with flake food and spirulina. As per their size, the best tank mates for Sparkling Gourmanis would be micro-sized ember tetras, rasboras, small cory cats, and otos.


14. Celestial Pearl Danio

Celestial Pearl Danio has confusing traits; they are semi-schooling fish breed. Sometimes they like to live and swim in groups and other times they don’t. It is better to keep them in the configuration of one male and the rest three or four females.

Celestial Pearl Danio has another name of galaxy rasbora. It is slim bodied and long in size. The fins of Celestial Pearl Danio are small with pointed tips. The color and design of the body are inquisitively beautiful. They come in a dark blue color, and on it, there are attractive golden spots everywhere.

The female Celestial Pearl Danio has bright orange color as their base on fins and tails. On the other hand, males have different catchy combinations. They have large red and black patches on their fins that give them a unique look.

These tiny fishes have a size of about 1-inch. Keep them stay in a nano tank of at least 10-gallon capacity. When talking about their temperament, males are dominative, and they can create uncomfortable zones over the issue of mating rights. Also, you must provide Celestial Pearl Danio with an ample number of hiding places. This fish can have tank mates, including all the fishes belonging to Danio species.

The water temperature best suited for them is 22-26°C. Also, the tank water should have a pH level of 6.5-7.5. These easy-going fishes are omnivorous by nature; therefore, their diet includes flake food, live or frozen food, and micro pallets, of course.


15. Rummy Nose Tetra

Rummy Nose Tetras are the fishes native to the Amazon River Basin. They are one of the best choices for the fishes in nano tanks. It is not only advantageous that they are small in size, but are beautiful creatures to look at.

The exciting thing about these fishes is that they have a vivid number of colors of their head. Also, the body of Rummy Nose Tetra is almost transparent. It lets you see the bones of the fish somehow. But the head is of hue red. Even its tail is unique; it has stripes in black and white colors.

This quirky look from head to tail makes Rummy Nose Tetras very eye-catchy. Its appearance has made it quite popular among the aquarist community. As it belongs to the Tetra breed, it does well in groups. Rummy Nose Tetras is a passive creature with a calm nature. Hence, these fishes are most suited with tank mates such as Hatchetfish, Mollis, Harlequin Rasbora, and Cherry Barbs.

Another attractive trait about Rummy Nose Tetra is that they like to stay in the middle column of the water tank. They swim periodically to all sides but prefer to settle in the middle of the aquarium at the end.

Rummy Nose Tetras are omnivores and can eat anything. You can have plants for them inside the aquarium so that they can eat and suffice in between the meals. This breed of fish usually sizes up to 2.5-inches. They require more space than regular freshwater nano tank fishes. You can have a water tank of about 20-gallon capacity for them, with a water temperature of 75-84°F and a pH level of about 6.4-7.0.


Things to Consider for Setting Up and Maintaining a Nano Tank for Freshwater Fishes:

Once you are done deciding the species of the fishes, it is time for you to set up their new home – the nano water tank. Here are some essentials that you must consider for your nano water tank installation and maintenance.


Nitrogen Cycle:

Starting with the cause, fishes poop & pee in tanks only. They do not have a proper space or what we say ‘toilet’ for them to excrete the waste out of their body. When they excrete, the solid substance sits on the bottom of the tank and starts to break inside the water. This substance produces ammonia, which is super harmful and toxic for the fishes to survive.

As more and more excreta gets out of the body of the fishes, the tank becomes a more hazardous place for them to live. Fortunately, there exist some bacteria that eat ammonia. These bacteria intake ammonia and convert it into nitrite and then nitrate, which is good for the living environment of your aquatic pets. This conversion of ammonia into nitrite and nitrate is called the nitrogen cycle.

However, it takes time for the bacteria to work on ammonia, so, meanwhile, fishes may become ill, or can even die due to excessive ammonia or nitrite presence. Therefore, you must change the water of your tank regularly.


Size of the Tank:

It is one of the most vital factors to consider when petting fishes. All the basic items depend upon the size of the tank, such as how many fishes you can keep, what plants you can have in your tank, how much space is the tank going to cover, and how often you would have to maintain it.

If you are thinking that having a tiny aquarium, such as a nano tank, would require less maintenance, then you are wrong. Since there will be less water in the tank, you would have to change it frequently, even for a single fish.

It is better to go for a tank of at least 10 gallons of capacity or more. In this way, there will be more amount of water for the waste to get diluted in. Also, you will be able to get the time off to change the water of the aquarium more often.



It can be challenging to find the right filter for your nano tank. You need to find a filter that does its work in the measurement of one gallon per hour (GPH). For instance, if you have a tank of 10-gallon capacity, you should have a filter of at least 40 GPH. Also, make sure that your filtration unit has a gentle flow. In this way, it would not disturb the swim of the fast fishes and flow of the small and light-weighted fishes.



The decoration of your tank majorly depends on the species of fish that you have. Some fishes require an abundance of plants to swim inside out of them and have their way. Others might want no or fewer plants. These fishes like to enjoy the open area to swim all their way. You might also need caves or hidings for the fishes, as some need their privacy.

So, you can have your way with decoration according to the fishes’ requirements and adaptations. Each of the types has many possible ways of decorating the tank.

What are Nano Tanks?

Nano tanks have become extremely popular for the past few years. They come in different structures, configurations, and choices. They are most preferred because they are easily affordable and can fit around anywhere. Nano tanks serve you as a piece of decoration too, where you can pet your favorite fishes.

Some people also like to beautify the ecosystem of the nano tanks for their tiny aquatic pets. You can use live plants in it, add a small fountain range, or equip it with a bubble sprinkler. If you wish, you can set up an entire miniature form of a garden in the nano tank.

Now, as already said, the decorations are fine in a nano tank, but what about the fishes. Not all the fishes can live in a nano-sized tank. Therefore, you will have to consider a few things while getting your fishes. The following are some stunning options of small freshwater fishes that you can get for your nano tank.


It does not matter if you have a large aquatic tank, or a nano tank, everything is feasible. You only need to make the right decision for the fishes, as all of them may have different delicacies. Nano tanks are compatible and affordable. So, don’t limit your imagination to its size & try to have a great experience in your nano tank with freshwater fishes.

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