Top 10 Nano Freshwater Fish

Small things are cute, tiny are even cutier

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Scarlet Badis ( Dario Drio )

Origin: India


Maximum Size: .75” to 1”

Minimum Tank Size: 5 gallons for one fish, 10 gallons for a pair

Diet: Difficult to feed dried foods and should therefore be fed a variety of live and frozen food including brine shrimp, banana worms, and daphnia. Badids tend to develop diseases and become obese when fed bloodworms and tubifex worms so these should be omitted from their diet.

The scarlet badis is a stunning nano fish that has a body shape strikingly similar to that of dwarf cichlids, although there is no relation. The scarlet gem is a timid fish and very peaceful with other fish of similar size and temperament. Its best to house one male Scarlet Badis per every 5 gallons as they can be aggressive towards each other. Due to their shy and timid nature, care should be taken to ensure that they are properly fed. The scarlet badis makes for a unique addition to a small community tank. Find out more about the Scarlet Gem here!


Pygmy Cory Cats (Corydoras sp.)

Origin: South America

pH: 6.5-7.6

Maximum Size: 1.3”

Minimum Tank Size: 5 gallons

Diet: Omnivorous and will accept a variety of sinking foods as well as frozen food such as tubifex and bloodworms. Corydoras should never be expected to survive on the uneaten food from other tank mates and are not cleaners of an aquarium by any means.

Each of these tiny cory cats is cuter than the last and all of them originate from South America. The tail spot (C. hastatus) and pygmy cory (C. pygmaeus) will likely max out at about one inch in length, while the salt and pepper cory (C. hasbrosus) will grow to be only three-quarters of an inch long.

Pygmy corydoras are peaceful and schooling and should be kept in groups of 3-6 individuals. The different Corydora species will likely school together as well. The majority of the species in the Corydoras genus are bottom dwellers, however these mini corydoras prefer to swim in the middle levels of the water as well as the lower levels.

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Pea Puffer (Carinotetraodon travancoricus)

Origin: Southern India

pH: 7.0-7.6

Maximum Size: 1”

Minimum Tank Size: 5 gallons, preferably 10 gallons if housing 3 or more

Diet: Carnivorous, feeding primarily only small crustaceans, mollusks, and worms in the wild and will do best on a diet of frozen brine shrimp, krill, and bloodworms. Live snails should be given regularly to help keep their sharp teeth ground down, which grow continuously.

Yes, there is such a thing as freshwater puffer fish! In fact, there are several species of freshwater puffers, but this one is the smallest (and the cutest!) and can be kept in a tank as small as 5 gallons. Pea puffers max out at just over an inch in size and should only be grouped with each other, small catfish, and small gobies such as the bumble bee goby. Despite their very tiny size they can be quite aggressive and do not make suitable tankmates for other small, free-swimming fish and can be difficult to house with larger species as well. Pea puffers can also be aggressive towards each other and care should be taken to house a 1:2 ratio of males to females and no more than 3 puffers should be housed in a 5-gallon tank.

Pea puffers will do best in a tank that is heavily planted with plenty of hiding spaces and places for this curious fish to explore. Puffers are a delight to have in aquarium; they are very inquisitive and will often swim up to the glass when you approach the tank. As with all puffer fish it has the ability to inflate its stomach with water or air when threatened, puffing up to two to three times its size.

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Otocinclus Catfish (Otocinclus sp.)

Origin: South America

pH: 6.8-7.5

Maximum Size: 2”

Minimum Tank Size: 5 gallons

Diet:  Herbivorous, primarily will consume naturally growing algae in an aquarium, but will need to be supplemented as algae is eaten with algae based flakes, pellets, or wafers.

The Otocinclus catfish is one of the best and favorite algae eaters in the hobby. It does a really great job at keeping your aquarium glass, décor, and plants free of algae. The ‘Oto’ catfish is one of the smallest catfish in the Loricariidae family. These little lawn mowers have a fierce appetite and will require an algae supplement in the form of a flake or wafer if there is not enough algae present in the aquarium.

Otocinclus catfish are very peaceful and can be introduced into a number of different communities. They are a schooling fish and will do better in small groups of 2 to 6 individuals.

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Green Neon Rasbora (Microdevario kubotai)

The green neon or yellow neon rasbora (Microdevario kubotai) is another sparkling gem from Southeast Asia’s rainforest rivers, where it occurs in small schools. Whether the color appears green or yellow depends on how the light is reflecting off the fish and, to some extent, how you see color.

Whatever color it appears, this is a beautiful fish in a tiny package. Females can reach about ¾ inch (2 cm), while the slenderer and more colorful males will stay smaller. Males will display to each other, as well as to females, so they’re also interesting behaviorally. Keeping a group of these is sure to make them one of your favorite fish.

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Trigonostigma Espei

Temperature: 23 – 28 °C

pH: 5.5 – 7.5

Standard Length

25 – 30 mm.

Its range is known to extend at least as far as the Prek Tuk Sap river basin near the coastal town of Sihanoukville in southwestern Cambodia while reports from Laos probably represent cases of mistaken identity. More recently a population has been discovered on the nearby island of Phu Quoc, Vietnam.

The colour of the fish can vary depending on the locality; for example specimens from Krabi province, south Thailand have a more intense reddish colouration than those from Chanthaburi province in the east.

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Galaxy Danio (Celestichthys margaritatus)

The galaxy or fireworks danio (Celestichthys margaritatus) has just about everything you could want from a fish. This species is breathtakingly beautiful, easy to breed, and simple to maintain. It is, however, a true nano fish, with the largest females not reaching an inch (2.5 cm) and the more colorful and slenderer males remaining even smaller. Taxonomically, this species is rather a mess, as the original description was rushed in part so the author could impose the common name “celestial pearl danio.” Well, scientists don’t get to choose common names; collectors, exporters, importers, and hobbyists get to do that. Besides, we already have a pearl danio, and it’s a very nice fish in its own right. Subsequent scientific study invalidated the genus Celestichthys and moved the fish into the genus Danio. Later work revalidated Celestichthys and returned the fish to that genus, where it currently resides.

The color pattern is truly reminiscent of a nighttime sky or even fireworks. I personally prefer the name “fireworks rasbora” because of the squiggly lines that appear on the body and in the fins. Whatever you call it, this species is ideally suited to a nano aquarium. It is an egg scatterer and will spawn in the aquarium, particularly among fineleaved plants. It does like to hide among floating vegetation but does not require that to thrive.

It is possible that a few fry will grow up in the tank with the adults, but the chances for that seem to be higher in larger tanks with more hiding places. This species shoals rather than schools and some intra-species aggression will be seen. Males will fight with each other and display to females. They may occasionally nip each other’s fins.

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Chili Rasbora (Boraras brigittae)

This list could easily have been dominated by the genus Boraras, with all its members being tiny living jewels that fit well into most nano aquariums. Limiting myself to one member of the genus means that I must choose the fish I believe to be the most beautiful and striking of the genus, B. brigittae. This fish has many common names, including chili rasbora, mosquito rasbora, and Brigitte rasbora. Whichever one is used, the name will be longer than the fish, which does not reach ¾ inch (2 cm).
The most prominent features are the teardrop-shaped horizontal markings surrounded by electric orange. The males are more colorful, while females tend to be larger and more robust. Pound for pound, or more accurately, milligram for milligram, this just might be the best aquarium fish we have. The colors are breathtakingly beautiful, the fish are completely peaceful, and they do great in a planted aquarium. Despite occurring in blackwater in nature, they are highly adaptable and will do well in almost any water conditions in the aquarium. When purchasing this species, don’t be fooled by the imitations. B. urophthalmoides is frequently sold as B. brigittae. It sports a similar black marking, but it does not have any of the orange that makes B. brigittae so distinctive. Sometimes, mixed groups of B. brigittae and B. merah will be sold as B. brigittae.
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Sundadanio Axelrodi


Maximum Size: 0.75” to 1”

Minimum Tank Size: 5 gallons

Diet: Omnivorous and will accept a variety of small pelleted foods as well as high quality flakes and freeze dried snacks including bloodworms, daphnia, tubifex, and brine shrimp. As always it is good to feed a varied diet that includes frozen foods.

Oh, the micro rasboras! They are the tiniest of the tiny and there are so many different varieties of them. I have listed 7 of my favorites commonly stocked at Absolutely Fish.  All of these micro cyprinids are very peaceful, active, and schooling fish and would do best if stocked in groups of 5-6 or more. Many of them are also very shy and will show their best personalities if provided with plenty of hiding places and a large school to make them feel safe.

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Ember Tetra (Hyphessobrycon amandae)

Origin: South America


Maximum Size: ¾ of an inch

Minimum Tank Size: 5 gallons

Diet: Will do well on a diet of small dried foods such as micro pellets and flakes. Should be supplemented with frozen brine shrimp, tubifex worms, and planktonic foods.

The Amanda Tetras, also known as Ember tetras look like tiny floating flames when placed in a school in a tank with darker substrate. Ember tetras are an active, very peaceful schooling fish and would do best in groups of 5 or more. They are native to soft water and would do best in slightly acidic waters, although they are capable of adapting to a range of hardness. Great mid-level swimming fish and will school with other small tetras such as neon tetras.


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