22 Best Nano Freshwater Fish For Nano Tanks

Sparkling Gourami

Many nano fish have become so popular and the most kept species in freshwater aquariums and there is an obvious reason for this.

To clarify, a nano fish is any fish that is small enough to thrive in a tank that is no more than 20 gallons.

Many hobbyists prefer keeping them because they will just require a conveniently sized nano tank.

Nano tanks don’t take much space and are considered as small investments. When first getting into the hobby, many people prefer starting small and testing things out.

This guide is intended to give the list of the best nano freshwater fish you can have in your nano tank because I know how overwhelming it can be to find what will suit your passion and needs.

The Rummy Nose teras is one of the best-looking tetras despite lacking many color splashes. Their design is simple but alluring.

They have a nice torpedo-shaped body, and apart from the head and tail its completely transparent. Due to that you can see through the fish and notice its bones.

What truly makes them stand out are its head and tail. The head is covered in a fiery red hue, and yes that’s where the name came from.

The tail is covered in a zebra-like black and white stripes creating a very nice and attention-grabbing mismatch.

A school of Rummy Nose tetras is always discernable in any community tank. You can always see that fiery red-colored head cruising in your tank.

Rummy Nose tetras are schooling fish and like any classic schooling fish, they will not do well if not kept in a decently sized school. A minimum of 6 Rummy Nose tetras is recommended, but more is always better.

Giving that they only grow to a maximum size of just 2.5 inches you can conveniently allocate 2 gallons of space per fish. That means you can have 8 to 10 of them in a 20-gallon tank.

Rummy Nose Tetras are one of the most recommended nano fish for beginners due to their peacefulness, hardiness, and adorable schooling behavior. They are also quite sturdy in the sense that they rarely get sick.

That said, they are a bit sensitive to temperature and pH fluctuations.

Rummy Nose Tetra

Rummy Nose Tetra Care Snippet

  • Maximum fish size: 2.5 inch
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Minimum Tank Size: 20 gallons
  • Temperature: 75–84 °F 
  • PH: 6.2 to 7.0
  • Hardness: 2-10 KH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Other Small tetras, Danios, Corydoras, Mollies, Hatchetfish.

Ember Tetra

Ember Tetra hardly reach 1 inch in size making them the smallest tetra and one of the smallest nano fish in the aquarium space. They also have lots of desirable qualities which make them ideal for a hobbyist of all experience level.

Most of them come in a striking orange hue that put a splash of orange almost like no other species. What is interesting is most of their body is transparent allowing you to see their bones just like the Rummy Nose Tetra.

In a heavily planted tank, a school of Ember Tetras look sensational- someone describes it like watching orange bullets move in slow motion.

If you are someone who wants to have no more than a 10-gallons tank and still want a schooling fish, I recommend you go for them. 

They are nano fish that that do not produce a ton of waste. So, you can get away with keeping 8 Ember Tetras in a 10-gallon tank.

As long as you have at least 7 of these little guys you should see them being very active in your tank. They are active schooling fish that will liven up your tank. But they will avoid coming out in the open, if they are not in a decently sized school.

Finally, you should be careful in choosing tank mates for them. Remember they are even smaller than the already small Neon Tetra. Many fish could mistake them for food.

Two ember Tetras swimming in a heavily vegetated tank

Ember Tetra Care Snippet

  • Maximum fish size: 1.0 inch
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 10 gallons
  • Temperament: Peaceful
  • Temperature: 73°F to 84°F
  • PH: 5.0 to 7.0
  • Hardness: 5-17dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Dwarf Gourami, Pygmy Corydoras, Rasbora, Hachetfish, Discus, Barbs

The Chili Rasbora look a bit similar with the previously mentioned Ember Tetra in terms of appearance. They also have a maximum size of about 1 inch but are slimmer than the Ember Tetras.

They come from the well-known Rasbora family and are the second smallest species in the family- only bigger than the Dwarf Rasbora.

They also have an attention-grabbing orange coloration but can sometimes come in red. Their body also has a nice touch of black creating a very classy look.

Chili Rasboras are schooling fish too and feel more comfortable in a considerably sized school. They will appreciate a school of at least 8.

Though some aquarists reckoned that a 5-gallon tank is the minimum tank for the Chili Rasbora I think 10-gallon should be the minimum.

In a 10-gallon tank, you can have a school of 10 to 12 Chili Rasbora. 

Next to being in a properly sized school they need lots of aquarium vegetation. Try using a mix of easy-care floating and planting plants.

Other tank decorations like driftwoods and pieces of rocks will make them adapt easier.

Chili Rasboras swimming in a heavily planted tank

Chili Rasbora Care Snippet

  • Maximum fish Size: 0.8 inch
  • Aquarist Experience Level: Beginner – Expert
  • Minimum tank size: 10 gallons
  • Aquarist Experience Level: Medium
  • Temperament: Peaceful
  • Temperature: 65-72°F
  • PH: 6.0 to 7.0
  • Hardness: 2-3dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal Tank Mates: Ember Tetra, Pygmy Corydoras, Toucan Tetras, Bolivian Ram 

Neon Tetra

The Neon Tetra is so darn popular in the aquarium space so much that it has been estimated around 2 million are sold monthly in the US alone. 

They have become that popular because they rack up so many desirable qualities.

Firstly, they are nano fish that can successfully live in nano tanks that are not out of reach of most fish hobbyists. They grow to a maximum size of just 1.5 inches making them one of the smallest schooling fish you can find.

Secondly, they are undoubtfully one of the most colorful freshwater fish around. Their body is covered in a vibrant red and blue hue which is where the name came from.

Thanks to that iridescent red and blue stripe, they can stand out in any community tank. Except where their rivalled cousin; the Cardinal tetra is present (the main reason why they are mistaken for one another).

Thirdly, Neon Tetras is quite hardy compared to many freshwater species. They are relatively easy to care for. One thing you need to ensure is only place them in a properly cycled tank.

Lastly, like most tetras, they are also quite passive. So, in terms of tankmate selection, you have lots of options.

It’s a good thing that they are schooling fish as they look even more awesome in groups. I recommend you have a minimum of 8 neon tetras together, but 15-20 is always better.

Their tiny size and striking colors make them so mesmerizing to look at, you will just see flashes of red and blue move in your tank.

It’s highly recommended you equip their tank with lots of vegetation using a combination of floating plants such as Hornwort and planting plants such as Java Fern.

Neon Tetra swimming in a nicely planted tank

Neon Tetra Care Snippet

  • Maximum fish size: 1.5 inch 
  • Aquarist Experience Level: Beginners – Expert
  • Minimum tank size: 10 gallons
  • Temperament: Peaceful
  • Temperature: 70°F to 81°F 
  • PH: Below 7.0
  • Hardness: Below 10dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Ember Tetras, Dwarf Gourami, Pygmy Corydoras, Chili Rasbora, Hachetfish, Guppies, Kuhli Loach

Cardinal Tetra

This is the fish that is very similar in both appearance and requirements with the Neon Tetra. The differences between the two in terms of appearance is that, Cardinal tetra is slightly bigger and its red stripe extend from head to tail.

Even though it grows bigger than the Neon, the Cardinal Tetra is still a conveniently sized nano fish considering it grows to a maximum size of 2 inches.

With this size, you can successfully have a school of 10 cardinal tetras in a small 20-gallons tank.

Some advantages that this fish has over the Neon Tetra is that it is less susceptible to diseases, provided it is kept in an ideal tank conditions.

Also, its iridescent red and blue stripe in most cases is slightly more vibrant than that of the Neons.

To give them a chance at thriving, provide a tank that closely mimics their habitat conditions.

That means they want a tank with lots of vegetation and hiding places. All these won’t matter much if you only have 3 of these little guys. Consequently, its recommended you have a school of at least 8.

Due to their peaceful nature, you also have lots of other passive species in their size bracket you can choose as their tank mates.

A Cardinal Tetra

Cardinal Tetra Care Snippet

  • Maximum fish size: 2 inch
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Minimum Tank Size: 15 gallons
  • Temperature: 73–81°F
  • PH:  6.0–7.0
  • Hardness: Up to 4 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Hatchetfish, Danios, Guppies, Loaches, Platies, Small Barbs etc.

Betta Splendens

Bettas have become so popular due to their distinctive beautiful look, incredible hardiness and wait for it- aggression. When this fish is spoken of, people are mostly referring to the males.

Yes, the males are more gorgeous looking thanks to their long flowing fin that looks as if they are floating in the wind. Also, their body colors are usually more vibrant.

That is not to say that the females aren’t beautiful, they are also unique in their own way.

Bettas come in some many color variations with one to suit everyone, effectively making them one of the most colorful freshwater species out there.

In terms of hardiness, they can survive poor water conditions that most freshwater species could not. They even have a special organ that helps them survive poorly oxygenated water.

Regardless, you should always provide the ideal conditions. Just because they can survive a condition does not mean they will thrive in it.

Bettas are highly aggressive and territorial, they are called Siamese fighting fish for a reason. This shouldn’t be a turn off for you, because as long as you avoid keeping males together it should be fine.

Two or more females can often live without a problem.

Unlike tetras, Bettas are not schooling fish and will happily live a solo life. For this reason and their hardiness, they are one of the best options for nano tanks even though they are outside the range of nano fish.

A male betta can successfully live in just a 5-gallon tank. Try doing that with cardinal tetras.

A male Betta; one of the best fish for a 5 gallon tank

Betta Splendens Care Snippet

  • Maximum fish size: 3 inch
  • Aquarist Experience Level: Beginners – Expert
  • Minimum tank size: 5 gallons
  • Temperament: Aggressive and Territorial
  • Temperature: 72 °F to 86 °F but most optimal is 78 °F to 80 °F
  • PH: Around 7.0
  • Hardness: 5.0 – 20.0 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Mollies, Kuhli Loach, Otocinclus.

Harlequin Rasbora

The Harlequin Rasbora is a nano fish from the Rasbora Family. They have become one of the most recommended nano fish for beginners due to their incredible hardiness, ease of care and lovely appearance.

They have a simple diamond-shaped body covered in a striking pinkish-orange hue and a contrasting black patch extending from dorsal fin to tail.

They are more popular than the previously mentioned Chili Rasbora because they are sturdier and rarely get affected by diseases. That is provided they are kept in ideal water conditions.

Harlequin Rasbora are active schooling fish that grow to a maximum size of 2 inches. It’s highly recommended you keep no less than a school of 8 of these guys and a 20 gallon will serve that number.

Harlequin Rasbora

Harlequin Rasbora Care Snippet

  • Maximum fish size: 2 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginners – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 72–81°F
  • PH:  6.0–7.5
  • Hardness: Up to 12 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetra, Danios, Guppies, Loaches, Platies, Small Barbs etc.

Cherry barbs are another nano fish that does well in small tanks. Normally this fish is covered in silver/black coloration with a golden silver lateral line.

But during the breeding period, the males turn to a vibrant cherry-like red coloration which where they got their name.

Thanks to that transformation they have become of the most colorful freshwater species around. They look absolutely fascinating, especially in a well-planted tank.

Cherry barbs are also schooling fish and will become stressed out if kept in small groups or singly. It’s recommended you keep a minimum school of 5.

Considering they only grow to a maximum size of just 2 inches you can house that number in just a 10-gallons tank.

All things considered, they are easy to care for and ideal for beginners. Its important you mimic their habitat conditions as closely as possible.

Considering they originated from streams and ponds of the rainforest floor they will appreciate a dimly lit tank. Try making use of easy care aquarium plants such as Java Moss, Anacharis, Hornwort and so on.

Other tank decorations such as driftwoods and pieces of rocks would help as well.

Cherry Barb

Cherry Barb Care Snippet

  • Maximum fish size: 2 inch
  • Minimum tank size: 20 gallons
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Temperature: 73 °F to 81 °F
  • PH: 6.0 to 8.0
  • Hardness: 5.0 – 19.0 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Cardinal Tetra, Ember Tetra, Chili Rasbora, Mollies, Kuhli Loach, Otocinclus.

Fancy Guppy

Fancy guppy is one of the most colorful freshwater fish that can thrive in nano tanks. They come in a variety of amazing colors, so it’s not an exaggeration to say that there is a color for everyone.

In terms of body shape, the best way to describe them is a stretched out betta. Like betta, they too have a fan-like tail and the males are also more colorful than females.

As opposed to Tetras, Danios and Rasboras, Guppies are not schooling fish. That is not to say they hate the company. They too are social fish and will feel lonely if kept alone.

They will do fine starting with a group of just 3.

Surprisingly, male guppies are smaller than the females. The males have a size range of 0.6 to 1.4 inches while the females have a size range of 1.2 to 2.4 inches.

If you want to add interesting splashes of colors to your tank and you don’t want to have more than a 5-gallon tank, Guppies are your best bet. In a 5-gallons tank, you can have trio guppies (males obviously).

However, if you want to have both male and females I recommend you go for a minimum of 20-gallons tank because they tend to make lots of babies.

A very vibrant colored Guppy

Fancy Guppies Care Snippet

  • Maximum fish size: Male 1.5 inch, Female 2.4 inch
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful but males may be aggressive to other males
  • Minimum tank size: 10 gallons
  • Temperature: 74 to 82 °F (24 to 28°C)
  • PH: 6.5 to 7.0
  • Hardness: 5-12 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Cory Catfish, Mollies, Zebra Loaches, Platies.

Endler’s Livebearers

The endlers livebearers are rare species of guppies which is why they are very similar in terms of body appearance.

Their males grow to a maximum size of about an 1 inch while the females can reach up to 1.8 inches in size.

They are nano fish that add a touch of interesting colors in a small tank. With so many variations out there its hard to not find a color that will suit you.

Like many species, the males are more vibrant then females. This is the major reason why many hobbyists prefer keeping the males. 

However, it’s rewarding to keep both genders because these fish breed very easily.

In many cases, they conveniently pair off without any interference from the owners. They give birth to a free-swimming fry, which is why they are called livebearers.

In case you plan on keeping both sexes make sure to have at least 2 females per male. This will lower aggression between the males and also help reduce the pressure on the few females during breeding.

And in that case, settle not for nothing less than a 20-gallons tank.

It’s important to refrain from keeping both endler’s livebearers and guppies in the same tank to prevent cross-breeding.

Finally, they also require a tank with lots of plants, try to use hardy ones such as java fern or java moss.

Endlers Livebearers

Endlers Livebearers Care Snippet

  • Maximum fish size: Male 1 inch, Female 1.8 inch
  • Minimum tank size:20 gallons
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Temperature: 75 – 86°F (24 – 30°C)
  • PH: 7.0 — 8.5
  • Hardness: ‎15 — 35°H
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Cory Catfish, Honey Gourami, Zebra Danio, Chili Rasbora.

Zebra Danio

Zebra danio is a very active schooling fish that does very well in nano tanks. Like Cardinal Tetras, they also grow to a maximum size of just 2 inches.

As the name suggests, they have Zebra like color pattern on their body which surprisingly put on a good show when they are hurtling in a tank.

Their body is covered in beautiful stripes of gold, white or silver contrasted by another stripe of black, dark green or indigo hue.

Zebra danios are very active and will explore all the sections of the tank provided they are in large groups.

However, if kept in a skimpy sized school they will become less active and will generally stick to swimming in the middle section of the tank. When this happens, they become stressed out and become more vulnerable to diseases.

Although a 10-gallon tank can keep a school of 5 Zebra Danios, it’s better to go for a 15 gallons or a 20 gallon.

For the most part, these fish are peaceful. Two things to point out however is, one-they tend to exhibit social hierarchy in the sense that a dominant fish always emerge among their group.

Don’t worry because that is actually playful and hardly results in an injury. 

Secondly, Zebra Danios are known to nip at slow-moving long-finned species such as Betta. So it’s a good idea to not house them with those kind of fish.

A Zebra Danion (Danio rerio)

Zebra Danios Care Snippet

  • Maximum fish size: 2 inch
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Minimum Tank Size: 10 gallons
  • Temperature: 64–74°F (18–24°C)
  • PH: 6.0–8.0 p
  • Hardness: 5.0–19.0 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Tetras, Guppies, Mollies, Platies, Barbs, Plecos.

Bluefin Notho

Bluefin Notho is a nano species of freshwater annual killifish that originated from Mozambique but are now seen in marshes throughout Africa. They are annual because they only appear during rainy season. 

Fortunately, in captivity, they are known to live for up to 2 years with proper care. Due to the considerable short lifespan, they tend to mature very quickly. Luckily they are also very easy to breed.

Bluefin Notho are kept by many hobbyists mostly due to their fascinating body coloration. They come in a variety of colors and patterns but their males are mostly covered in light red, neon blue and black.

The females on the hand are usually dimmer and mostly covered in a slightly shimmering silver hue.

They grow to a maximum size of about 2.4 inches and are perfect for nano tanks seeing as you can keep as little as you want.

Bluefin Notho

Bluefin Notho Care Snippet

  • Maximum fish size: 2.4 inch
  • Minimum tank size:10 gallons
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Mostly Peaceful but males can be aggressive to each other
  • Temperature: 70-75°F
  • PH: 6.0-7.0
  • Hardness: 2-5 dGH
  • Diet: Omnivore
  • Care Level: Medium
  • Ideal tank mates: Tetras, Rasboras, Gourami, Livebearers, Small Barbs, Dwarf Cichlid, et Cetra

White Cloud Minnows

The white cloud mountain minnows resemble the Neon Tetra in both color and personality. Due to this and the fact that they are more affordable than the neon, they are sometimes called the “common mans neon”.

These fish are among the most recommended nano fish for beginners. They are quite hardy and can survive a varying range of water conditions.

That said, you have to avoid very warm temperature because they originated from a cool mountainous region, so they are more used to cool temperatures.

The white cloud mountain minnows are also schooling fish and need to be kept in a group of at least 5. Seeing as they only grow to a maximum size of about 1.5 inches, a small 10-gallon tank should be the minimum.

In that 10-gallons tank, you can safely have a school of 6.

Temperament wise, they are quite peaceful and will do well with lots of other similar sized peaceful species.

White Cloud Minnows

White Cloud Minnows Care Snippet

  • Maximum fish size: 1.5 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginners – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 18–22 °C (64–72 °F) can also survive temperature as low as 5 °C (41 °F)
  • PH: 6.0 to 8.0
  • Hardness: 5-19 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetra, Harlequin Rasbora, Chili Rasbora, Livebearers, Corydoras.

Celestial Pearl Danio

Also called the Galaxy Rasbora for their impeccable galaxy like color design. This freshwater fish was recently discovered (in 2006 to be precise) in a small plant laden spring-fed pool in the southeast Asian nation of Burma.

Their body contains beautiful white spots and an outstanding looking fins covered either in red or orange hue complementing the rest of the body. Their belly is covered in the same striking fin color.

This color mix and design makes the celestial pearl danio one of the most visually appealing nano freshwater fish.

It’s an interesting fact that at the time this fish was discovered and its photo stated circulating online, many people didn’t believe it was real. They thought how could such a spectacular looking fish have been missed this whole time.

These fish is undoubtfully one of the best options for someone that wants and a splash of colors in their tank. Like the Ember Tetras they only grow to about an inch, but they aren’t schooling fish.

Nevertheless, they still appreciate some company and it’s important you have the correct male to female ratio.

If you keep more males they will fight each other, plus they will put pressure on the few females. A good rule is to have 3 females per male.

The celestial pearl danio needs a heavily planted tank with lots of hiding places due to the nature of where they originated from. They won’t survive in a skimpy decorated and planted tank.

To a large extent, they are peaceful and will leave peacefully with other passive species.

But make sure you don’t have a fish big enough to bully or mistake them for food.

Celestial Pearl Danio swimming in a heavily planted tank

Celestial Pearl Danio Care Snippet

  • Maximum fish size: 1.0 inch
  • Minimum tank size: 10 gallons
  • Aquarist Experience Level: Beginners – Expert
  • Temperament: Peaceful
  • Temperature: 73°F to 79°F
  • PH: 6.8 to 8.4
  • Hardness: 5-10dGH
  • Diet: Omnivore
  • Care Level: Relatively easy
  • Ideal tank mates: Neon Tetra, Ember TetraChili Rasbora, Guppies, Cory Catfish, Sparkling Gourami, Honey Gourami, Mollies, et Cetra

Sparkling Gourami

The Sparkling Gourami has become so well known in the aquarium space and for good reasons. To start with, they are beautiful.

Their body sparkle (as the name suggests) which make them among the best options for anyone that wants to add a splash of colors to their tank.

They are one of the most peaceful gouramis around, for that reason, they aren’t so limiting in terms of tank mate selection.

Like bettas, sparkling gourami have what’s called the labyrinth organ which enables them to take in oxygen directly if the water condition is poor. They are quite hardy and tolerate a varying range of water conditions.

Their size makes them ideal for most hobbyists keeping. They grow to a maximum size of just 1.6 inches and are not fast swimmers.

Additionally, they are not schooling fish and will be fine in a group of just four. This makes them very ideal for nano tanks. A small 10 gallons-tank will be able to house 4 sparkling gouramis.

When you consider their peacefulness, hardiness, colorfulness and relative small size, its not hard to realise why they are kept by aquarists of all experience level.

It’s important to make sure you provide them with a heavily planted tank because they are used to that kind of environment. Bright light is something they are also not used to.

Sparkling Gourami

Sparkling Gourami Care Snippet

  • Maximum fish size: 1.6 inch 
  • Minimum tank size: 15 gallons
  • Aquarist Experience Level: Beginner – Expert
  • Temperament: Mostly Peaceful but males will be aggressive to each other
  • Temperature: 71.5°F to 80.5°F 
  • PH: Below 6.5 to 7.0
  • Hardness: 2 to 5 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Platies, Swordtails, Ember Tetras, Zebra Danios, Neon Tetras, Dwarf Gourami, Pygmy Corydoras, Chili Rasbora, Hachetfish, Guppies, Kuhli Loachet Cetra

Pygmy Corydora

If you want a highly peaceful and super easy to care for bottom dweller that will do well in a nano tank, the Pygmy Corydora might be just the fish for you. 

They are nano fish from the catfish family. Their size ranges from 0.7.5 to 1.3 inches.

Unlike a bottom-dwelling species like the Kuhli Loachpygmy Corydoras are known to swim in a shoal to the upper part of the tank occasionally.

This is important to note because some people think of them as complete bottom dwellers. For that reason, they introduce other species that occupy the middle and topmost part of the tank without considering the cory.

Interestingly, pygmy corys can move to the surface of the water and use their intestine to take in oxygen directly when the water condition is bad.

Consequently, it could be a problem if they get hindered by species occupying the middle or topmost part of the tank.

Pygmy corys need to be kept in a group of at least 4 and a small 10-gallon tank can conveniently house that number. They also need lots of vegetation and other tank decoration to provide them the hiding spaces they need.

Even though they spend most of their time scavenging for food at the bottom of the tank they are not classic algae eaters. They prefer a protein-based diet and can not survive only on algae and leftovers from other fish.

Pygmy Corydora resting on a driftwood

Pygmy Corydora Care Snippet

  • Maximum fish size: 1.0 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 72 °F to 79 °F
  • PH: 6.5 to 7.5
  • Hardness2.0 – 25.0 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Marbled Hatchetfish, Kuhli Loach, Otocinclus, Shrimp, Snails, etc.

Otocinclus

Now these are the classic algae eaters and one of the best you can have in a nano tank. 

They are known as “dwarf suckers” and they grow to a maximum size of just 2 inches.

These fish spend most of their time at the bottom of the tank sucking up any algae they can find on different surfaces of plants and decorations. It is adorable to watch (it is more fun to watch them from the underside of the tank) because they do the algae sucking in a group.

The fact that they are avid algae eaters doesn’t mean they can survive on just algae. They still require their diet to be supplemented with some plant-based matters.

They are herbivores and will happily snack on algae wafers and other vegetable matters such as peas.

Otocinlus are extremely reserved species, as such, it is a good idea to combine them with only peaceful species within their size bracket.  

Overall they are easy to care for and ideal for beginners.

Otocinclus Care Snippet

  • Maximum fish size: 2.0 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 72 to 82°F
  • PH: 6.0 to 7.5
  • Hardness: 5dH – 15dH
  • Diet: Herbivores
  • Care Level: Relatively Easy
  • Ideal tank mates: Corydoras Catfish, Danios, Dwarf Gourami, Guppies, Harlequin Rasbora, Mollies, Tetras, Zebra Loaches, et Cetra.
An Otocinclus resting on a plant

Least Killifish

Despite having the word “Killifish” in their name, least killifish is not a true killifish. Its is an underrated livebearing species that originated from the lower coastal plain between North Carolina and Southern Louisiana.

Surprisingly, they originated from the family housing some of the most popular freshwater species like Guppies Mollys and Swordtails.

Least killifish is one of the few species that can thrive in nano tanks such as a 5 gallon or a 10-gallons tank. 

They have a size range of between 0.5 to 1.2 inches which is why they are considered as one of the smallest aquarium fish species right now.

Whilst least killifish are known to shoal they generally prefer living in small groups without any other fish. They will do very well in a group of just 5.

It’s worth noting that they tend to breed easily. If you are keeping both sexes, breeding is bound to occur in which case you will need to provide a separate tank or move them to a bigger one.

Heterandria formosa

Least Killifish Care Snippet

  • Maximum fish size: 1.2 inch
  • Temperament: Shy and peaceful
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 5 Gallons
  • Temperature: 66 and 75°F
  • PH: Around 7.0
  • Hardness 5-20 dH 
  • Diet: Omnivorous
  • Care Level: Easy
  • Ideal tank mates: Neon Tetras, Marbled Hatchetfish, Kuhli Loach, Otocinclus, Ember Tetra, Chili Rasbora 

Bumblebee Goby

The Bumblebee Goby originated from the Brachygobius Genus and is a small bottom-dwelling fish with size range from 0.6 to 1.5 inches. This fish has a very appealing bee-like yellow and black stripe pattern.

Thanks to their unique body appearance, they can stand out in aquariums despite their tiny size. Many hobbyists keep these fish due to their charming social behavior.

Though they can be shy when first introduced in a tank, that changes very quickly if they have all they require in the tank.

They are playful little fish and their males are usually territorial. This is why you will see every male trying to claim his area in the tank. As a result, territorial hassle usually develops among them, you will see them chasing one another.

But don’t worry, that hardly result in any injury and is fun to watch.

Regrettably, Bumblebee Goby is not a good choice for most community tanks for two reasons. 

Firstly, although they are sold as freshwater fish they actually require a tank set up with brackish water. 

To be precise, they require brackish water with low salt grade- a salinity between 1.002 and 1.006

Secondly, they will easily get out-competed for food by most species due to their size.

Undeterred by these challenges, bumblebee goby is still one of the best fish for nano tanks for so many reasons.

The good news is that a freshwater verity of this fish does exist. It’s just that they are way less common than the brackish ones.

If you are keen on keeping them, make sure you know which is which and provide them with tank conditions similar to their habitats.

Bumblebee Goby Care Snippet

  • Maximum fish size: 1.5 inch
  • Temperament: Peaceful
  • Minimum Tank Size: 10 gallons
  • Aquarist Experience Level: Intermediate – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 72 °F to 84 °F
  • PH: 7.0 to 8.5
  • Hardness: 9.0 – 19.0 dKH
  • Diet: Omnivore
  • Care Level: Medium

Scarlet Badis

Scarlet Bardis is starting to become one of the most recommended fish for nano tanks. It’s not hard to see why if you consider their exquisite body coloration, tiny size and a rather peaceful temperament.

Their body is usually covered in a combination of a lighter and darker orange or red hue. A pattern of lighter color is complemented by darker vertical stripes. A bright neon blue accent can be found on the dorsal fins creating a very classy look.

With a maximum size of just 0.7 inches in most cases, Scarlet Badis are the tiniest nano fish on this list.

The only reason why these species might not be the best options for beginners is that they are somewhat demanding in terms of feeding. Plus, they require more tank cleaning routine than the average freshwater fish.

They require a heavily planted tank so that they have abundant hiding places to compensate for their timid personality.

Don’t let their tiny size underestimate their capability, they are quite aggressive to their kind. They are also micro predators and will hunt down small creatures they can find in your tank. 

For this reason, it is not a good idea to keep them with ornamental shrimp or any other pet within that size.  

Male and Female Scarlet Badis

Scarlet Badis Care Snippet

  • Maximum fish size: 0.8 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 10 gallons
  • Temperature: 72 °F to 79 °F
  • PH: 6.5 to 7.5
  • Hardness: 10 – 20.0 dGH
  • Diet: Omnivore

Marbled Hatchetfish

Marbled Hatchetfish is one of the most bizarre-looking nano fish. This unique looking fish has a body resembling, you guessed it- a hatchet.

A very distinct gold line stretch from its eye to its caudal fin. The area below the line is covered in a marble-like pattern of brown and cream hue. With these features, there is no chance of you mistaking your Hatchetfish for any of the fish on this list.

Fascinatingly, marbled hatchetfish is also a schooling fish. These fish show timid behavior almost like no other fish when not in groups. Naturally, they are shy and nervous, but that reduces when in large schools.

A minimum of 6 marbled hatchet fish is recommended.

They usually grow to a maximum size of about 1.4 inches but that does not mean a 10-gallon tank can suit them.

They also require lots of vegetation and hiding places to feel less agitated and for that reason, I recommend a minimum of 15-gallons tank. In a tank that size, you can keep 8 to 10 Marbled Hatchetfish.

Make sure you equip the tank with lots of floating plants like Hornwort seeing as they occupy the topmost part of the tank.

Again, a tight-fitting lid is a must-have due to their jumping habit.

I understand many hobbyists might be tempted to have these fish. But if you are a beginner I recommend skipping them.

The reason is they are highly susceptible to ich, and that timid behavior can interfere with their feeding need. They are more suited for intermediate to expert fish keepers.

Marbled Hatchetfish

Scarlet Badis Care Snippet

  • Maximum fish size: 2 inch
  • Aquarist Experience Level: Intermediate – Expert
  • Temperament: Peaceful
  • Minimum Tank Size: 15 gallons
  • Temperature: 75–80°F
  • PH: 5.5–7.0 p
  • Hardness: 4.0–12.0 dGH
  • Diet: Omnivore
  • Care Level: Moderate
  • Ideal tank mates: Small Tetras, Chili Rasbora, Kuhli Loach.

Peacock Gudgeon

The Peacock Gudgeon, also known as Peacock Goby or Peacock Eye Gudgeon is a tropical freshwater fish that originated from New Zealand, Papua New Guinea and Australia.

These fish have one of the most unique looking body forms on this list. They have slender bodies and a rounded head. They have elongated dorsal and anal fins that are more pronounced than most fish.

Suitably, they have nice body coloration that matches their distinctive form. They come in different color variations but most of the specimens have a striking blue background followed by bright red stripes.

Peacock Gudgeon has a maximum size of just 3 inches. They can live in single pairs successfully but prefer living in a group of 6 to 8.

Their relatively small size, ability to live in small groups, peacefulness and the fact that they are not good swimmers makes them a good option for nano tanks.

Peacock Gudgeon

Peacock Gudgeon Care Snippet

  • Maximum fish size: 3.0 inch
  • Temperament: Peaceful
  • Aquarist Experience Level: Beginner – Expert
  • Minimum Tank Size: 15 gallons
  • Temperature: 72 °F to 79 °F
  • PH: 6.0 to 7.2
  • Hardness: Up to 12 dGH
  • Diet: Omnivore
  • Care Level: Easy
  • Ideal tank mate: Ember Tetra, Cory Catfish, Kuhli Loach, Bumblebee Goby, Celestial Pearl Danio, Harlequin Rasbora, Cherry Barb

Things to consider before choosing a nano tank

Tank size

Nano tank stop at 10 gallons, but some consider 20 gallons a nano tank as well. I guess I do too. 

Some of the most popular sizes include 1 gallon, 3.4 gallons, 5 gallons, 10 gallons, 15 gallons and 20 gallons. Before selecting any fish, you have to decide what size do you want to go for.

For the record, I do not recommend anything less than 5 gallon tank. The 5 gallons too comes with lots of limitation. Although a small tank may seem easier to manage, that is not actually the case.

A small 5-gallons tank will require way more attention than say- a 10 or 20 gallon because it quickly becomes dirty. There isn’t just enough water to dilute the fish waste, which means more frequent water replacement has to be conducted.

Another problem with very small tanks is that changes in water parameters happen way quicker than in bigger tanks. The pH, temperature or other parameters can spike in a matter of minutes which can jeopardize your fish life.

For these reasons, I recommend going for at least 15 to 20-gallons tank if at all possible.

Fish size and behaviour

You have to make sure you are fully aware of the size and behavior of the species you selected. Are they a schooling fish? Can they live singly? Or how many of their number due they need to thrive?

You do not want to overcrowd your fish.

Nano Tanks Requirements

Filteration

Filtration is not something you want to skimp on, and it’s even more important when dealing with nano tanks. You need to find out your filters rating which is usually measured in gallon per hour (GPH).

It’s recommended to have a filter that has at least 4 times the capacity of your tank. Meaning, if you have a 20 gallons tank your filter should at least be 80 GPH.

Next to this is making sure your match your species with the appropriate filter flow rate. If your fish prefers gentle current make sure you use a filter that delivers water gently.

Substrate

You need to find out the best substrate that will suit your nano fish by finding out what they are used to in their habitat.

It’s also important to ensure you use a substrate that will support the live plants you plan to make use of. Some of the commons options are sand, gravel and soil.

Lighting

Lighting is more for the plants and ourselves than it is for the fish. They are used to facilitate plant growth and give the tank fascinating looks and make it easier to see the fish through the tank. 

In most cases, natural light is enough for the fish.

If you use artificial lighting make sure to adjust them so they can suit you and the plants, and at the same time not disturb the fish.

Heating

Most nano fish come from tropical regions and will need a heater. That said, you need to check the if that’s the case with your fish.

Plants and decorations

You can not rise a thriving community of fish without the help of live plants, that’s why choosing the appropriate one is so important. 

The key to achieving that is understanding the habitat of the nano fish you selected.

They are naturally used to vegetation so you want to make sure you make the tank somehow resemble the habitat through the use of planting and floating plants. Some of the most beginner-friendly plants for small tanks include:

  • Java Moss
  • Anubias Nana
  • Java Fern
  • Duckweed
  • Micro Swords
  • Marimo Moss balls

Other elements that are found in their habitat include rocks, caves, tree branches and so on. To mimic that too you can make use of pieces of rocks, driftwoods, caves in your tank as appropriate.

Closing

I’m sure by now you have realized that there is a lot you can do with a nano tank. With it, you can successfully keep a variety of nano fish which by the way are some of the most awesome species in the whole aquarium space.

I repeat- make sure you are fully aware of your fish requirements and set up the tank to take care of those needs. Remember to not overcrowd it and never skimp on the required water changes.

Which nano fish is your favourite? I will appreciate if you comment your answer below.

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