18 Small Freshwater Fish Best for Nano Tanks (+How Set Up Your Tank)

By Eddie Waithaka @aquariawise

18 Small Freshwater Fish Best for Nano Tanks (+How Set Up Your Tank)

Finding a small freshwater fish for a nano tank can be quite challenging given that most species grow to an adult size of 3 inches or more.

A regular sized goldfish, for example, though quite popular among fish keepers around thea world, will never fit in anything smaller than a 20-gallon aquarium. Neither will an average sized algae eater like the bristlenose pleco.

Even so, just because your tank is small doesn’t mean you won’t find a fish small enough to fit in it. There are a couple of species that are uniquely suited for nano tank environments.

They include cold water fish (red rose minnows, gold barbs, bloodfin tetras, white cloud minnows, Buenos Aires tetras,), nano tank schooling fish (neon tetras, amber tetras, guppies, zebra danios, harlequin rasboras), and 5 to 10-gallon species (dwarf gourami, honey gourami, betta, ghost shrimp, Amano shrimp, African dwarf frog, dwarf puffer fish, celestial pearl danio and more ).

Having said that, this article will explore each of the species mentioned above (and more) to help you choose one that will fit in your aquarium best.

We’ll also look at how to set up your nano tank albeit concisely.

But first…

What is Considered a Nano Tank?

There is somewhat of a grey area concerning the definition of the phrase, but most fish keepers consider and refer to an aquarium that is 10-gallons or less as a nano tank.

However, some still consider a nano tank to be anything from a 5-gallon and below, which include fish bowls.

But all in all, a fish tank that is only ideal for fish that are at most 3 inches can be considered a nano tank. Which means such an aquarium can only house a small school of schooling fish (like 6 Neon tetras) or one to two average size freshwater fish like dwarf gourami or betta.

Now let’s look at the 18 small freshwater fish best for nano tanks.

For the best insight and for your convenience, I’ve put the fish in 4 major groupings that are of most concern to hobbyist keeping fish in small (nano) tanks.

Group #1 — Nano Schooling Fish

This group includes 5 small fish species that exhibit schooling behavior and are tiny enough for a nano tank even in a group.

Neon Tetra

The neon tetra is a small species native to the clearwater streams in the Orinoco and Amazon basins of South America.

The fish grow to approximately 1.5 inches in overall length and is considered easy to keep in a community aquarium of at least 5 to 10 gallons.

An important rule of thumb when stocking this fish is to have 1 gallon of water for each linear inch of tetra.

Keep your neon tetras in a group of 6 or more individuals or in a community tank.

However, the fish are timid and because of their small size, should not be maintained with large or aggressive fish. Moreover, they are sensitive to water chemistry, so add them in a fully established tank.

Ember Tetra

The ember tetra is another fish from the tetra family that makes a good candidate for nano tanks.

The species is of typical tetra shape but grows to a maximum length of approximately 0.8 inches, which is fairly smaller than the neon tetra.

For this reason, a group of 6 embers can even fit in a 5-gallon, though a 10-gallon fish tank is safer and easier to maintain.

Same as the neon cousins, add 1 gallon of water for every inch of fish you add to your aquarium. Ember tetras should be maintained in a group of at least 4 to 6 individuals to promote schooling.

They also appreciate a heavily planted aquarium with a dark substrate and open water for swimming.


Also known as millionfish or rainbowfish, guppies are one of the world most widely distributed tropical fish and one of the most popular freshwater aquarium fish species.

The size of guppies vary, but usually males grow to between 0.6 and 1.4 inches, while females are 1.2 to 2.4 inches long.

Even so, a variety of guppy strains are produced by breeders through selective breeding characterised by different colors, patterns, shapes, and most importantly sizes.

Therefore, the average fish may vary from one breed to another.

Guppies should not be kept as a single fish in an aquarium because both male and female fish show signs of shoaling.

The fish also exhibit prolific breeding and can reproduce in both freshwater and marine aquaria.

Zebra Danios

The zebra danio is a species of active fish that are quite durable and can withstand an impressive range of water temperature and conditions.

The fish are also prolific breeders and among the easiest egg-layers to breed.

Zebra danios grow to an average length of 2 inches hence a group can only live in at least 10-gallons of water space. They are also schooling fish, so keep them in a group of 5 fishes or more.

Unlike most freshwater species which prefer tropical tanks conditions, zebra danios can live even in cold water hence they are one of the few species that can be maintained with goldfish.

The fish are a peaceful breed that get along with most tankmates, but they will nip fins on species with long flowing fins such as angelfish and betta.

Due to their active nature, they might stress slow fish as well, though they make good dither fish.

Harlequin Rasboras

Harlequin rasboras are a great example of an easy shoaling fish to add to your nano tank. They are easy to care for, prolific breeders, and perfect for a begginer.

The fish only grows to a maximum length of up to 2 inches thus a group will comfortably fit in a 10-gallon aquarium.

They are generally peaceful and good candidates for a community fish tank, plus they have excellent coloration good for when you want to add pomp to your fish tank.

In an aquarium, the fish are adapatable to different water parameters, and water chemistry is not critical provided that cleanliness of the tank is maintained.

Group #2 — Cold Water Nano Fish

This group includes fish species that can live in cold water nano tanks, and more so, can be maintained with goldfish.

The fishes preferred tank size range from 5 to 10 gallons.

Rosy Red Minnows

The fathead minnow is a species of temperate freshwater fish native to North America from Central Canada, east to Virginia and the North Eastern United States.

The rosyred minnow is a strain of the fathead that is quite popular and mostly kept as a feeder fish, but can also be maintained in an aquarium for its aesthetic value.

The male fish grows to between 2 and 3 inches long, while the female can grow up to 1 to 2 inches in length.

Rosy red minnows are hardy and will survive in water with little oxygen hence perfect for nano tanks.

For a suitable tank capacity for your fish, a 10-gallon tanks is recommended.

You can keep 4 to 6 ruby red minnows in a single aquarium as they are peaceful fish. Moreover, they are a schooling species and require to live in a group.

Since these fish are native to the temperate regions, they will adapt to nearly any temperature, with reports of the fish thriving at temperature below freezing and in temperatures as high as 100°F.

Bloodfin Tetras

The bloodfin tetra is a small and active fish of the characidae family, closely related to neon and ember tetras. These freshwater fish are perfect for beginner aquarists since they can stand a wide range of tank water parameters including cold water.

Like most aquarium tetras, these characins are fairly small reaching just under 2.5 inches hence perfect for your nano tank.

Keep them in at least a 10-gallon aquarium that is elongated and covered at the top, because the fish swim at the upper water layer and are capable of jumping out of the tank.

Bloodfins should be kept in a small school of 6 or more to keep them calm.

The fishcan survive in slightly acidic to alkaline water and will thrive in cooler water temperature between 70°F and 80°F. For this reason, they are sometimes kept in cold water aquariums or aquariums without a heater.

White Cloud Mountain Minnow

The white cloud mountain minnow is a hardy species of freshwater and coldwater fish often kept in aquariums. The fish are sold in the fish keeping trade under a variety of names including white cloud, white cloud minnow and white cloud mountain minnow.

The fish are small (only reaching a length of between 1 and 1.5 inches) and are famously nicknamed ‘The working man’s neon’ because they compare to neon tetras albeit less expensive.

White clouds will fit in a 5 to 10-gallon nano tank, and should be kept in a good-sized school, preferably of a half dozen or more individuals.

When maintained singly, white clouds tend to lose their color and hide most of the time.

They are peaceful as well hence will fit with other small, peaceful species in a community aquarium. Avoid larger fish as they will be inclined to eat your smaller Chinese minnows.

Often, they are sold as companions for goldfish due to both speices preferring colder water temperatures. However, goldies can and often snack on their smaller tank mates, so watch out and should you notice any of your white clouds missing, place them in a separate tank.

Golden Barb

The golden barb also known as the green,China or golden barb is a hardy species that can survive in a cold water nano tank. It’s native to South East Asia from China (Southern), Vietman to Laos.

Females are usually larger reaching up to 3 inches, though the species remain relatively small in the home aquarium and grow to a maximum length of 2.3 Inches.

That being said, most will only grow to about 2 inches especially when they are kept in smaller (nano) aquariums.

The gold barbs are peaceful and will do well in most community fish tanks. It’s tolerance to cold water and docile nature makes it one of the few good tank mates for goldfish.

Because of their aforementioned small size, you can comfortably keep them in a 10-gallon fish tank, but a larger tank will provide a healtheir and more stable environment for the barbs.

Group #3 — Small Freshwater Fish Best for 5-Gallon Nano Tank

Considering a nano tank can range anywhere from 0ne gallon to 10 gallons, it is imperative to determine which species can survive in the pretty tiny 5-gallon nano tanks.

Some good fish species for this size tanks include:

Betta Fish

The siamese fighting fish, commonly referred to as betta, is a popular freshwater species and a member of the larger gourami family.

Apart from the stunning colors, especially in male fish, fish keepers love betta fish because of their hardy nature and relatively small size.

The recommended minimum tank size for betta should be 5-gallons, but the fish will survive even in a 2.5-gallon nano aquarium. However, a smaller tank is difficult to keep clean and free of ammonia and other toxins.

That said, the siamese fighting fish is highly terrirotial and males in particular are prone to high levels of aggressions and will attack each other if housed in the same tank.

You can, however, maintain one male with 2 to 3 female betta, though you’ll need a big aquarium. A 5-gallon nano tank is only enough for a single betta.

Luckily, betta fish don’t get lonely when kept alone and they are not a schooling species, so a single fish in your tank will be fine.

Dwarf Puffer Fish

The dwarf puffer fish also called Malabar puffer, pea puffer fish or pygmy pufferfish is a small freshwater puffer native to Kerala and Southern Karnatak in South-West India.

Unlike other in the family, pea puffers live in freshwater nano aquariums. The fish grows to an adult size of about an inch in length and will comfortably fit in a 5-gallon aquarium.

However, if you plan to have more than one puffer, your are better off with a 10-gallon tank.

Add a generous amount of plants in your dwarf puffer tank to provide hiding places. Moreover, the fish is pretty curious, so be sure to give to give them plenty of entertainment.

Pygmy puffers are canivorous species, so a steady supply of meaty foods is necessary, and occasionaly feed them snails to keep the puffer’s sharp teeth ground down.

Endler Guppy

Poecilia wingei, know to aquarists as endlers or endler’s livebearers is a small fish native to the Pania peninsula in Venezuela. The fish is pretty good looking, peaceful and a prolific breeder hence a good addition to a beginners nano tank.

Endlers guppy males grow to an average length of less than an inch, while females can reach a maximum of 1.4 inches long, and will comfortably fit in your 5-gallon fish tank.

The dwarf guppy fishes are not only perfect nano tank inhabitants, but because of their actvie nature, its best to keep several couples at once.

They prefer small tanks with lentic water and thickly planted with various aquartic plants species, especially floating species.

That said, endlers readily breed with guppies, so you should avoid keeping them together if you don’t intend inter-breeding them.

Ghost Shrimp

Apart from freshwater fish, you can keep a host of inverts in your 5-gallon nano tank including freshwater aquarium shrimp.

A good freshwater shrimp to start with would be the ghost shrimp albeit the invert having a short lifespan of less than one year.

Also known as glass shrimp, thes inverts are excellent scavengers, and inexpensive, efficient aquarium cleaners that will devour any kind of left over food in the aquarium.

Ghost shrimp are relatively small reaching a maximum size of only 2 inches and a group can live in a 5-gallon aquarium.

Moreover, they are peaceful hence can live in a community tank with small and docile fishes like tetras and harlequin rasboras.

Even so, don’t maintain your ghost shrimp with large fish like goldfish or cichlids because they will become a quick snack for their bigger companions.

Amano Shrimp

Another easy shrimp you can keep in your nano tank is the Amano, also called Yamato, Japanese or Algae shrimp. It is native to Japan and Taiwan and is an excellent alage eater.

Amano shrimp will live in nearly any size tank as long as the regular rules of fish count are observed.

They like a habitat with a lot of live plants that provide hiding spaces and area for the shrimp to explore.

Usually, Amanos grow to an adult size of 1.5 to 2 inches and can live in a 5-gallon tank, though a 10-gallon is recommended when maintaining your shrimp in a large group or community aquarium.

As with any shrimp, only maintain your alage shrimp with small, docile fish that won’t snack on them.

Keep amano shrimp in your aquarium when you need a peaceful cleaning clue that will get rid of algae in your fish tank.

Group #4 — Small Freshwater Fish Best for 10-Gallon Nano Tank

If you have a slightly bigger aquarium than a 5-gallon, consider this species for you nano tank, best for a fish tank that is at least 10 gallons.

Pygmy Corydoras

If you are looking for a schooling fish with adorable looks, peaceful and fun to watch, plus one that will live in a fairly small aquarium, then pygmy corydoras (pygmy cory or pygmy catfish) are a perfect choice.

The fish are native to South America, mainly Rio Maderia in areas with plenty of hiding places in the form of plants and fallen braches.

Pygmy cories look like other corydaras, but they don’t grow bigger than an inch in length. For this reason, its possible to have 8 cories in a 10-gallon nano tank.

However, a larger group is better for the fish; if a shoal is not large enough, the fish often become skittish and stressed.

Moreover, a larger aquarium is better than a taller one.

Also, make sure you use a sand substrate to ensure your corie’s barbels don’t wear down, otherwise, the fish won’t be able to search for food.

The barbel may even rot, which is quite dangerous considering it is so close to the fish’s face.

Pygmy catfish will live with a host of species in a community, but they mostly prefer 2 to 3 species at most. And don’t do well in the presence of large, aggressive fish because of their fairly small size.

Dwarf Gourami

Almost like a drop of paint in your fish tank, dwarf gouramis come in all colors of the rainbow and are guaranteed to make your nano aquarium stand out.

They are also low maintenance, quite hardy and genreally peaceful and shy.

If you keep a pair of these fish, they will almost always swim together.

Dwarf gouramis are closely related to betta and are condidered labyrinth fish, which mean they breathe straight from the air.

Consequently, the lung-like labyrinth organ, coupled with a fairly medium size (4 to 4.5 inches) make these fish ideal for a small 10-gallon nano tank.

Popular dwarf gourami types include the blue dwarf, powder blue dwarf, flame dwarf, neon blue dwarf and the honey dwarf gourami.

The fish prefer relatively small, slow-flowing bodies of water with densely planrted beds, but the substrate for the fish does’nt play a huge role.

As for plants, free folating or drifting plants are your best choice. Floating species with fine leaves such as hornwort will help replicate their natural environment.

The fish are peaceful and tolerate neighbours and will live with other fish in a community. However, they prefer to be maintained in a tank with non-aggressive and relatively small fish with similar water chemistry requirements.

Celestial Pearl Danio

The celesrial pearl danio is a small freshwater fish found in small vegetative ponds in South Eat Asia.

They are suited for small tanks that are packed with plants and stocked with other colorful fish and mimic their peaceful nature.

The fishare timid and largely peaceful, they work perfectly in communities full of guppies, mollies and tetras.

Celestial pearl danios only grow to a maximum length of 1 inch hence a group of up to 8 individuals can be maintained in a 10-gallon nano tank.

However, beware of the sometimes combative behavior of dominant males when maintaining these danios in a school.

The fish prefer a dark substrate, and floating plants are a useful addition. Howbeit, driftwood, oak, beech or almond leaf are best avoided as the tannins they release are not a feature of the danios natural waters.

African Dwarf Frog

If you want to add something new and unique to your small (nano) aquarium, consider introducing a frog to the set up.

The African dwarf frogs small, peaceful creatures perfect for small community aquariums.

They are largely nocuturnal and can get pretty intresting to watch during the moonlit hours.

The frogs grow to an average of 3 inches and 1 or 2 individuals can live happily in a 5-gallon aquarium. But if you are getting more than a pair, or if they’ll be sharing the tank with fish, go for a 10 to 20-gallon fish tank.

Female African dwarf frogs are usually wider and males slimmers. However, be aware that these frogs are commonly confused with the larger African clawed frogs which grow quite big and require a bigger aquarium.

Another thing, African dwarf frogs are fully aquatic so you dont need to worry about maintaining a half-terrain tank.

Light in a dwarf frog fish tank is crucial as well, ergo ensure they get 10 to 12 hours of light a day. Plus their skin is sensitive to chemicals, so a good filter is a must.

How to Set Up Your Freshwater Nano Tank (Aquarium)

Nano tanks are popular, particularly since the set up and maintainance costs are low.

Moreover, given the quality products developed around this trend, adding a slice of nature to your house can never be easier.

Nonetheless, with a low internal volume, setting up a nano tank can be an up hill test, but that should not put you down.

Below is a quick set up guide.

A Quick Step by Step Nano Tank Set Up Guide

#1. Set your fish tank in the desired position, and because it is a nano tank, you can set it in a wider variety of places than most conventional aquariums. Even so, keep it away from direct sunlight, out of the reach of children and in a low traffic area.

#2. Add a layer of substrate (either sand or gravel depending on your fish) sloped slightly towards the back. Remember the substrate will release nitrogen during the first few weeks, so test for ammonia and nitrares before adding your fish.

#3. Add other accessories including wood. It’s always better to research a couple of nano tank designs to decide what layout to go for. However, don’t add wood or almond leaves if your fish prefer alkaline water because they release tannins that will lower your aquarium water ph.

#4. Slowly add water to your nano tank using an air line to minimize clouding. Leave the water level just above the substrate level if your are going to add plants in your fish tank.

#5. Place your plants in the tank using tweezers. Start with the background plants then move to the mid-ground species and lastly add the foreground plants.

#6. Top up the water in your nano tank (using the air line) until half full. The other half should be filled with a bucket into the rear filter chamber tanking care not to dislodge your plants.

#7. Instal your aquarium equipment including the light, filter and heater. Place the light using the clamp on the outer aquarium wall. After, switch on your filter ensuring your nozzle is directed for a full circulation.

#8. Let your tank mature and the useful bacteria colony establish before adding your fish or inverts. That said, not all fishes are ideal for new tanks, for example neon tetras are quite sensitive to the changes. Therefore, exert caution when stocking your tank for the first time.

8 Useful Tip for When Establishing a Nano Tank

Use this tips when establishing your nano tank, they will help you with some of the common challanges most new nano tank owners face.

Tip #1 — Plant it Heavily to Ensure Water Quality

Although with a generous filter media capacity your nano tank water quality will be good for a group of small fish, shrimp or snails, live plants will help reinforce the filter and ensure good water qualtiy.

Plant usually help fish by removing nutrients and adding oxygen.

Good plant options for nano tanks include cryptocoryne wendtii (gree), and mosses or anubias varieties as they remain small and grow slowly hence perfect for long term aquascapes.

Riccia is good but requires more maintanance than the slow growers, but you can consider cypts and hairgrass instead.

Tip #2 — What Maintenance is Needed?

To ensure stability in your nano tank, do at least one 50 percent water change weekly with dechlorinated and temperature-adjusted water.

There is a risk of using tap water because any change in water chemistry could impact the fish given the tank’s volume, so consider RO (re-mineralized) water.

That said, it good to note that buying a large continer of the RO water could be more cost effective than purchasing small amounts.

Tip #3 — Stock Small Bodied Fish

From an aesthetic perspective, a finer texture and small-bodied fish is better for a nano tank as it wont look cramped or outweigh your aquarium.

Also, combining the small fish with small plants will make your fish tank look more proportional because of the more appropriate sense of scale.

Tip #4 — Nano Tank Filter

In addition to making your nano tank look beautiful, it must also be functional, which means an aqurium filter is vital.

Choosing a filter for a small fish tank can, however, be challenging because filters are designed for bigger tanks, and will look odd in a nano set up.

Even so, sponge filters make an excellent choice for such set ups as they are quite low flow and will not suck up tiny fish and inverts.

But sponge filters are bulky and not exactly pretty to look at.

A small external filter with the flow reduced is also fine for most but the smallest aquariums. The glasswear filter outlets and inlets ensure minimal visual disturbance.

Moreover, some manufacturers have designed products specific for the nano market, so make sure your look out for small (nano) tank filters before you purchase a diffrent product.

Tip #5 — Nano Tank Heater

Putting a heater in a nano tank is almost as crucial as adding one to a big aquarium, especially if you intend to keep tropical fish species.

There are a couple of small aquarium heaters available in the market, though most have quality issues. Therefore, be careful when buying one rest the temperature in your tank will keep flucuating continuously.

Tip #6 — Nano Tank Light

Luckily, nano tank lights are considerably similar to the lights used in big aquariums, but planted nano set ups often require less light output.

Ergo, use less intense light to grow your plants; consider Led lights since they are more efficient than comparable T5s and last quite a bit longer.

Tip #7 — Consider Adding Wood to Better Spruce Your Nano Tank

Adding pre-soaked wood in your tank will spruce the aquascape of your aquarium, more so when contrasted with green plants.

The selected piece can either be left proturding from the water line to add an extra dimension, or submerged in water to hold everything down.

Even so, do not add wood if you are going to keep fish from a wild habitat that is clear of tannins.

Lastly, if you go for a smaller piece of wood, you can place the tank’s supplied clear cover particularly if you’ll keep top-dwelling fish in your nano aquarium.

Tip #8 — Can You Use C02 Injection in a Nano Tank?

Yes, you can dose your nano tank, but it is safer and more economical to use a liquid carbon product and provided you don’t overdose.

Overdosing can be toxic to freshwater aquarium species more so shrimp and snails.

If you are located in the USA (more so Florida) and are looking to buy tropical (freshwater ) mentioned in this or any other post (and more), check out Consolidated Fish Farms Inc.

Also Consider usingAquariawise Coupon Code for a 10 percent discount on eligible purchase. They are a great source for healthy aquarium fish, plus we get a small commission with no extra cost to you.

Have fun with your lady betta.

Enjoy your nano tanks and have fun with the small fish; All the best.

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