Small Freshwater Fish – 21 Popular Types

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Are you looking for some great new fish to add to your aquarium? Small freshwater fish are the most versatile options because you can keep them in small, medium, or even large aquariums!

There are so many small freshwater fish available in the hobby that choosing the perfect species can be quite a challenge! Well, this article will make your life a lot easier by introducing 21 amazing small fish species and giving you some great information on their care.

So let’s dive right in!

Why Keep Small Freshwater Fish?

There are many advantages to keeping small fish. The first, and most obvious advantage is that you can keep them in a relatively small aquarium. This is cheaper and easier to set up than a large tank, and obviously takes up less space in your home or office.

Keeping a community tank of small freshwater fish also means you can have more of each fish and more variety than if you kept larger species. Small fish tend to be cheaper than large fish, although they aren’t necessarily easier to keep.

21 Popular Small Aquarium Fish Species

Now that you know all the benefits of small fish keeping, it’s time to learn more about 21 awesome species for your freshwater aquarium! I’ll be providing a list of the following important facts and water parameters for each species:

  • Scientific Name
  • Common Names
  • Minimum Tank Size
  • Adult Size
  • Temperament
  • Care Level
  • Diet
  • Origin
  • Temperature
  • Swimming Level

Let’s get started!

1. Chili Rasboras

  • Scientific Name: Boraras brigittae
  • Common Names: Mosquito rasbora
  • Minimum Tank Size: 10 gallons
  • Adult Size: 0.75 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Borneo, Southeast Asia
  • Temperature: 68-82°F
  • pH: 4-7

Chili rasboras are awesome schooling fish for a small aquarium. These micro fish don’t even reach an inch in length, so you never have to worry about them outgrowing your tank.

Chili rasboras feel safer in numbers, so make sure you pick up a big group of 10 or more. Keeping them in a nature-style tank with live plants will also bring out the best in them and make for a fascinating display.

2. Exclamation Point Rasbora

  • Scientific Name: Boraras urophthalmoides
  • Common Names: Least rasbora
  • Minimum Tank Size: 10 gallon
  • Adult Size: 0.5 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Thailand, Vietnam, Cambodia
  • Temperature: 68-82°F
  • pH: 6-7

The exclamation point rasbora is closely related to the chilli rasbora, but stays even smaller! They are the smallest of the rasboras in the aquarium trade, and the tiniest fish you are likely to come across.

Exclamation point rasboras get their name from the bold stripe and dot markings they have on the sides of their orange bodies. Exclamation point rasboras can be kept in a 5-gallon tank but will be much happier in a large school in a 10-gallon tank.

3. Scarlet Badis

  • Scientific Name: Dario dario
  • Common names: Scarlet gem badis
  • Minimum Tank Size: 5 gallon
  • Adult Size: 0.5-0.75 inches
  • Temperament: Semi-aggressive
  • Care Level: Moderate
  • Diet: Carnivore
  • Origin: India
  • Temperature: 64-79°F
  • pH: 6.5-7.5

The scarlet badis is an amazing little fish for more experienced aquarists. These micro fish look like tiny cichlids and they can be just as territorial. Scarlet badis are pretty shy and they require live foods, which is why they are not ideal for beginners.

They can be kept in a tank with other fish of the same species, but you’ll want to provide plenty of cover to prevent too much aggression. A group of one male with a few females is the ideal setup in a nano tank.

4. Neon Tetra

  • Scientific Name: Paracheirodon innesi
  • Common Names: Neon tetra
  • Minimum Tank Size: 15 gallons
  • Adult Size: 1 inch
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Brazil, Colombia, Peru
  • Temperature: 70-77°F
  • pH: 4-7.5

Neon tetras hardly need any introduction. These beautiful schooling fish are superstars of the aquarium world, and they are ideal for a community tank.

Neon tetras are super easy to care for and they will thrive on a diet of flake food. They are social creatures, however, so keep at least 6 to see all that these fish have to offer.

5. Endler’s Livebearers

  • Scientific Name: Poecilia wingei
  • Common names: Endler’s guppy
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1-1.8 inch
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Omnivore
  • Origin: Venezuela
  • Temperature: 75-86°F
  • pH: 7-8.5

Endler’s livebearers are great fish for beginners who do not have the room for a large fish tank. These fascinating fish have amazing colors, and beautiful fins, and they are really easy to breed!

Male Endler’s livebearers have amazing multi-colored markings, particularly in orange and black. The females are pretty plain in comparison, and also grow much larger.

6. Pygmy Cory Catfish

  • Scientific Name: Corydoras pygmaeus
  • Common Names: Pygmy corydoras
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1.2 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Brazil
  • Temperature: 72-79°F
  • pH: 6.4-7.4

The pygmy cory catfish is just one of the dozens of corydoras species in the aquarium hobby. These peaceful fish are much smaller than most other cories, however, and also have the interesting habit of schooling in the mid-water, rather than on the bottom.

These nano fish are really peaceful and will get along great with other nano schooling fish.

7. Betta Fish

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  • Scientific Name: Betta splendens
  • Common Names: Siamese fighting fish
  • Minimum Tank Size: 5 gallons
  • Adult Size: 2.5 inches
  • Temperament: Aggressive
  • Care Level: Moderate
  • Diet: Carnivore
  • Origin: Thailand
  • Temperature: 72-86°F
  • pH: 6-8

Betta fish are one of the best-looking fish species on the planet. These fish are available in a huge variety of different breed types and colors, so there’s a perfect betta for everyone!

Betta fish are not as small as some of the other nano fish on this list, but they do great in small aquariums. These fish should not be kept in small spaces like cups or bowls, but they can thrive in a 5-gallon tank with filtration and heating.

Betta fish are famously aggressive towards other bettas, but they can actually be kept with some other peaceful tank mates in a well-planned community tank.

8. Pea Puffers

  • Scientific Name: Carinotetraodon travancoricus
  • Common Names: Dwarf puffer
  • Minimum Tank Size: 5 gallons
  • Adult Size: 1 inch
  • Temperament: Semi-aggressive
  • Care Level: Moderate
  • Diet: Carnivore
  • Origin: India
  • Temperature: 72-82°F
  • pH: 6-8

If you’re looking for a small fish with a big personality, look no further than the pea puffer! These tiny fish can be kept in a very small tank, where they will amaze you with their adorable looks but ruthless attitude.

Pea puffers use their razor-sharp teeth to tear into aquarium snails, their favorite food! They are not great community fish, however, because they are known to bite their freshwater aquarium tank mates.

9. Honey Gourami

  • Scientific Name: Trichogaster chuna/ Colisa chuna
  • Common Names: Honey dwarf gourami, sunset gourami
  • Minimum Tank Size: 15 gallons
  • Adult Size: 2 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: India, Bangladesh, Nepal
  • Temperature: 72-81°F
  • pH: 6-7.5

The honey gourami is a beautiful fish from the betta family. These fish are relatively peaceful and can be kept alone as a centerpiece fish, although they will be happier if kept in a small group with plenty of hiding spaces. They also get along great with other species of peaceful community fish like tetras.

Honey gouramis are air-breathing fish, so they need to have access to the surface of the water to survive. These interesting fish also have two long feelers that they can use to explore their environment.

10. Ember Tetra

  • Scientific Name: Hyphessobrycon amandae
  • Common Names: Fire tetra, Amanda’s tetra, dwarf red tetra, red tetra
  • Minimum Tank Size: 10 gallons
  • Adult Size: 0.75 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Brazil
  • Temperature: 68-82°F
  • pH: 5-7

The ember tetra is one of the smallest tetra species in the aquarium hobby. These nano fish are a fiery red color but have very sweet personalities.

These very small fish can be pretty shy so keep a nice big school in a heavily planted tank to increase their confidence. Ember tetras are easy to care for and will thrive on a diet of crushed flakes and micro pellets.

11. Guppy Fish

  • Scientific Name: Poecilia reticulata
  • Common Names: Millionfish, rainbow fish, fancy guppies
  • Minimum Tank Size: 10 gallons
  • Adult Size: 2.5 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Omnivore
  • Origin: South America
  • Temperature: 63-82°F
  • pH: 7-8.5

Guppies are such popular aquarium fish that you’ll find them in just about any fish-keeping store you walk into. They are great beginner fish but still hold interest for expert aquarists interested in breeding projects.

There are many different breeds of guppies and these are generally known as fancy guppies. These fish are livebearers, which means they are really easy to breed.

12. Japanese Rice Fish

  • Scientific Name: Oryzias latipes
  • Common Names: Medaka, Japanese killifish
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1.25 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Japan, Taiwan, China, Vietnam, Laos
  • Temperature: 61-75°F
  • pH: 7-8

Japanese rice fish are awesome cold water fish for a nano tank. These shoaling fish are very peaceful and have been kept by fish keepers for centuries. There are many different breeds of Japanese rice fish, including white, pink, and orange types.

13. Cherry Barb

  • Scientific Name: Puntius titteya
  • Common Names: Cherry barb
  • Minimum Tank Size: 15 gallons
  • Adult Size: 2 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Omnivore
  • Origin: Sri Lanka
  • Temperature: 68-81°F
  • pH: 6-8

The cherry barb is a classic in the aquarium hobby. They get their name from the beautiful deep red color of the males in their breeding colors, although the females are also very attractive.

Cherry barbs are such popular freshwater fish because they get along great with other freshwater nano fish species. They do not have the fin-nipping tendencies of some other species like tiger barbs.

14. Black Neon Tetra

  • Scientific Name: Hyphessobrycon herbertaxelrodi
  • Common Names: Black neon
  • Minimum Tank Size: 15 gallons
  • Adult Size: 1.25 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Brazil
  • Temperature: 68-82°F
  • pH: 5-7.5

Black neon tetras make the perfect beginner fish for tropical freshwater aquariums. These small fish are incredibly peaceful, so they make an ideal tank mate for other fish.

Black neon tetras are very easy-going and hardy too. They thrive on a diet of flake food, but they will appreciate the occasional treat of live/frozen flake food.

15. Hatchet Fish

  • Scientific Name: Carnegiella strigata
  • Common Names: Marble hatchet
  • Minimum Tank Size: 20 gallons
  • Adult Size: 1.25 inches
  • Temperament: Peaceful
  • Care Level: Moderate
  • Diet: Carnivore
  • Origin: South America
  • Temperature: 68-82°F
  • pH: 5.5-7

The marble hatchet fish is a really unusual nano aquarium fish that will add life to the top level of your tank. These fish have a really deep, flattened body with interesting black markings and long pectoral fins that they hold above their backs.

Hatchet fish are master jumpers, so make sure your tank is completely sealed to prevent them from escaping. It is best to keep them in a school of ten or more and provide them with plenty of floating plants to bring out their confidence.

16. Harlequin Rasbora

  • Scientific Name: Trigonostigma heteromorpha
  • Common Names: Harlequin, Red rasbora
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1.5 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: omnivore
  • Origin: Southeast Asia
  • Temperature: 70-82°F
  • pH: 5-7.5

The harlequin rasbora is a peaceful schooling fish with characteristic black triangular markings on the back half of its body. This contrasts with their overall golden orange color to make for a mesmerizing display.

Harlequin rasboras are ideal community fish that get along great with other species of peaceful fish. These fish are great for beginners and will really thrive in a planted tank, especially if kept in a big school of ten or more.

17. Clown Killifish

  • Scientific Name: Epiplatys annulatus
  • Common Names: Rocket killifish
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1.25 inches
  • Temperament: Peaceful
  • Care Level: Moderate
  • Diet: Carnivore
  • Origin: Guinea and Sierra Leone, West Africa
  • Temperature: 68-79°F
  • pH: 5-7

The clown killifish (video source) is a slender banded fish that spends all its time up at the top of the aquarium. Once they color up, these tiny fish show the most amazing colors, especially on their tails.

These awesome nano fish are also known as rocket killifish because their tails look like the bright flames of a jet! Clown killifish can also rocket their way out of your tank, so make sure you have a tight-fitting lid to prevent them from jumping out.

18. Glolight Danio

  • Scientific Name: Celestichthys choprae
  • Common Names: glolight danio
  • Minimum Tank Size: 20 gallons
  • Adult Size: 1.25 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: Myanmar
  • Temperature: 61-82°F
  • pH: 6-8

Glolight danios are amazing golden fish from Southeast Asia. These hardy and adaptable fish should be kept in a nice big school of the same species. They are very active little fish, so they need a larger tank to really thrive.

19. Celestial Pearl Danio

  • Scientific Name: Celestichthys margaritatus
  • Common Names: Galaxy rasbora
  • Minimum Tank Size: 10 gallons
  • Adult Size: 0.8 inches
  • Temperament: Peaceful
  • Care Level: Moderate
  • Diet: Omnivore
  • Origin: Myanmar
  • Temperature: 68-79°F
  • pH: 6.5-7.5

Celestial pearl danios are one of the most beautiful freshwater fish for small tanks. These peaceful fish have vivid orange and black fins, and their bodies are covered in golden spots, just like a sparkling night sky. The females are a little less colorful than males, but they are still great-looking fish.

Celestial pearl danios are pretty shy little fish that thrive in a planted tank. They can be kept with other peaceful nano fish and will do best when kept with bottom and surface dwellers that won’t compete for their space in the midwater of the tank.

20. White Cloud Mountain Minnow

  • Scientific Name: Tanichthys albonubes
  • Common Names: White cloud minnow
  • Minimum Tank Size: 10 gallons
  • Adult Size: 1.5 inches
  • Temperament: Peaceful
  • Care Level: Easy
  • Diet: Carnivore
  • Origin: China
  • Temperature: 57-71°F
  • pH: 6-8.5

White cloud mountain minnows are very peaceful fish from the mountains of China. These small freshwater fish come from a cold water environment, so they do best when kept in an unheated freshwater tank.

Most white cloud mountain minnows have a neon silvery stripe down their sides and short, bright red fins. Some awesome new varieties are available, however, including a long-finned and a golden form.

21. Otocinclus Catfish

  • Scientific Name: Otocinclus sp.
  • Common Names: Oto, dwarf sucker
  • Minimum Tank Size: 10 gallons
  • Adult Size: 2 inches
  • Temperament: Peaceful
  • Care Level: Moderate
  • Diet: Algae
  • Origin: South America
  • Temperature: 74-79°F
  • pH: 6.8-7.5

Otocinclus catfish deserve a spot in just about any freshwater aquarium. These tiny fish are incredibly peaceful, which makes them the first choice for red cherry shrimp keepers.

These schooling fish are best known for eating algae, and they do an amazing job of keeping their tank clean.

Tank Setup for Small Fish

The best way to keep any freshwater nano fish is to create a tank that simulates its natural habitat. Continue reading to learn how!

Tank Size

Tank size can be a controversial issue when it comes to keeping nano fish. Some aquarists are able to keep fish in very small tanks, but this is can be very risky because water temperature and other parameters can swing very quickly in such a low volume.

The general rule is to provide as much space as possible for any fish, but most of the species on this list will thrive in a nano tank of 15 gallons or so if it is correctly set up. Of course, you can also keep small fish in large tanks.

Even the smallest aquarium fish can be great jumpers, so you will need a securely fitting hood/lid, no matter which tank size you choose.

Filtration

Once you have your tank picked out, you’re going to need to purchase a good-quality water filter. A small sponge filter or hang-on-back filter is an affordable option for beginners, but make sure the current isn’t blowing your fish around too much in a small tank.

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A canister filter is the best choice for planted display tanks, however, because they contain much more filtration media and are housed externally, and don’t take up any space in the tank.

For fish keepers and breeders with multiple tanks, air-powered sponge filters are a very affordable option.

Heating

Most fish keepers will need to use an aquarium heater to keep the water temperature warm enough for tropical fish. Heaters come in various sizes, however, so make sure to pick out a model that matches your tank size.

Some popular aquarium fish prefer cooler water temperatures and will be happier in an unheated aquarium. Japanese ricefish and white cloud mountain minnows are good examples of these coldwater aquarium fish.

Lighting

Your fish need a natural day/night cycle to remain healthy. Set your aquarium lights on a timer to create a natural rhythm, this way you’ll never forget to switch them on or off.

Growing live plants requires good lighting, although not all plants have the same lighting needs. Your tank should never be placed near a window where it receives direct sunlight.

Substrate and Decor

The fun really starts after you have put together all the ‘hardware’! Adding substrate and decorating your tank with hardscape and ornaments is what changes your aquarium from a glass box into an underwater world for your fish.

Dark, natural-colored substrates are always a great choice because they bring out the best colors in your fish. Use aquarium-safe sand or gravel only, and remember to rinse out the dust thoroughly before adding the substrate to your tank.

Adding some driftwood and rocks to the aquarium will create some structure and hiding spaces for your fish. Take care to pack heavy objects carefully, of course, because they can hurt your fish or damage your tank if they fall over.

Live Plants

Growing live plants is a great way to provide your fish with more natural habitats. Some of the benefits of growing live plants include:

  • Increased oxygen levels
  • Great hiding spaces
  • Decreased nitrate levels
  • Natural food sources like microorganisms

A tank full of green plants looks great too, and many aquarium plants are surprisingly easy to care for. If you’re new to growing live plants, start out with some easy epiphytes like Java ferns and Anubias. These plants can be kept in their pots or attached to your hardscape and can grow well under standard aquarium lighting.

Caring For Small fish

Caring for your small fish is not necessarily easier than caring for larger fish. In fact, maintaining a nano aquarium requires more care and attention. Read on to learn more about keeping your fish healthy.

Water Quality & Maintenance

Maintaining high water quality is your number one priority when keeping a small tank. Water parameters can change very quickly in a small aquarium, so make sure you test your water regularly.

Perform regular partial water changes to keep your nitrate levels below 20 ppm or so. Remember to use a water conditioner to neutralize your tap water, however, because it usually contains chemicals like chlorine or chloramine.

Feeding Your Fish

Providing your fish with a healthy, balanced diet is essential to keep them in great condition. Most nano fish are predominantly carnivorous and feed on tiny creatures such as insect larvae. Providing this kind of food regularly can be difficult, so most fishkeepers prefer to use prepared foods that contain all the protein, nutrients, and minerals that fish need.

Most of the fish in this article will thrive on a diet of prepared foods like crushed flake food or floating or sinking pellets. Providing live/frozen foods like baby brine shrimp, blood worms, or micro worms is recommended as an occasional treat, although some species like scarlet badis may need to be fed these natural foods on a daily basis.

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Otocinclus catfish are specialist algae eaters that will not feed on fish flakes. They will eat the algae that grow naturally in your tank, but they will need to be fed vegetables and/or algae wafers in a new aquarium with little algae growth.

Choosing Small Fish Tank Mates

Setting up a small fish community tank can is one of the most exciting parts of fish keeping, but it’s very important that all your fish get along.

Most small fish live in large schools or shoals in nature. They can be stressed, shy, and sometimes even aggressive if kept on their own or in very small groups in aquariums. Most species should be kept in groups of at least 6, although 10, 20, or more in the same tank would be even better!

Small fish should only be kept with other small fish that are not big enough to swallow each other. Each species should also be happy in the same range of water parameters like pH and temperature.

Some fish do great without any other tank mates, however. Keeping more aggressive fish like male betta fish and pea puffers on their own is generally recommended.

Where To Buy Small Freshwater Fish

Most of the small freshwater fish in this list can be found down at your local fish store. If you prefer the convenience of online shopping, I would highly recommend you check out our recommended list of vendors.

FAQs

What is the smallest pet fish?

The tiniest freshwater fish are the rasboras from the Boraras genus. At just half an inch or so, the exclamation point rasbora is the smallest freshwater species you’re likely to find for your aquarium!

What is a nano fish?

Nano fish are very small species that can be kept in a small aquarium. There is no strict rule, but fish that stay under about 2 inches long can be called nano fish.

What fish do well in a small tank?

Most nano fish do well in a small tank. The best species for small tanks are those that can be kept on their own or in small groups, however. Species like betta fish, scarlet badis, and pea puffers all do well in a 5-gallon tank or larger.

What fish can go in a 1-gallon tank?

A 1-gallon tank is too small to safely keep fresh water fish. Some aquarists are able to keep bettas in a tiny tank of that size but 5 gallons or more would be a safer and easier option.

What is the easiest fish to take care of in a small tank?

The betta fish is the easiest fish to care for in a small tank. These wonderful tropical fish do best when kept on their own in a small aquarium with a filter and a heater.

Final Thoughts

There is an amazing diversity of small freshwater fish species available to the modern aquarist. This can make deciding which species will work best in your tank kind of daunting, so why not choose from the 21 amazing species in this article? You won’t be disappointed!

Do you keep small freshwater fish? Tell us about your favorite small fish species in the comments below!

by Mark

Mark is the founder of Aquarium Store Depot. He started in the aquarium hobby at the age of 11 and along the way worked at local fish stores. He has kept freshwater tanks, ponds, and reef tanks for over 25 years. His site was created to share his knowledge and unique teaching style on a larger scale. He has worked on making aquarium and pond keeping approachable. Mark has been featured in two books about aquarium keeping - both best sellers on Amazon. Each year, he continues to help his readers and clients with knowledge, professional builds, and troubleshooting.

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