Animal
Neon tetra
The neon tetra is a tiny fish with a shiny blue stripe and a red stripe. It lives in forest streams in South America.
The neon tetra is a tiny fish, about as long as a quarter is wide, with a glowing blue stripe and a bright red patch. In the wild it lives in clear and dark-water forest streams of the western Amazon. It is also one of the most popular aquarium fish in the world.
Paracheirodon innesi is a small characin of terra firme forest streams in the western Amazon basin. Its iridescent blue stripe is a structural color that shifts with light levels. It is one of the most popular aquarium fishes, but the IUCN assesses it as Least Concern, because its wild habitats are well preserved and most fish in the trade are bred in captivity.
Photo: Holger Krisp, CC BY 3.0, via Wikimedia Commons
Meet the neon tetra
The neon tetra is a very small fish.
It is shorter than your finger. A blue stripe shines along its side, like a tiny light. Below it, the back half of its body is red.
The neon tetra is a small freshwater fish that grows to about 2.5 centimeters long, not counting its tail. That is about as long as a US quarter is wide.
Its most famous feature is a shining blue-green stripe that runs along its side. Below the stripe, the back half of its body is bright red. Neon tetras come from forest streams in South America, and they have become one of the best-known aquarium fish in the world.
Paracheirodon innesi is a characin (order Characiformes). The IUCN places it in the family Characidae, while FishBase now uses a newer grouping, the American tetras (Acestrorhamphidae). FishBase gives a maximum standard length of 2.5 centimeters.
The iridescent stripe along each side is not made by pigment. It is a structural color, produced by stacks of light-reflecting platelets inside cells called iridophores, and it changes in response to the brightness of the surroundings. Below it, the rear half of the body is red. The species was described in 1936, and a 1997 study cited by the IUCN ranked it, together with the guppy, as the most popular fish in the US aquarium hobby.
Quick facts
- Group
- Fish
- Length
- up to 2.5 cm
Where it lives
Wild neon tetras live in South America.
They swim in small streams in the rainforest. Some streams are clear, and some are dark brown, like tea.
In the wild, neon tetras live in the western part of the Amazon basin, in Brazil, Colombia and Peru. They swim in small forest streams that flow into the Solimões River.
Some of these streams have clear water, and some are blackwater streams, naturally dark brown like tea. The water is warm, soft and slightly acidic. The neon tetras sold in pet stores mostly come from fish farms, not from these streams.
The IUCN gives the native range as the western Amazon basin, in Brazil, Colombia and Peru, where the species occurs in terra firme streams (forest streams beyond the reach of river floods) with clear or dark water. FishBase describes it from blackwater or clearwater tributaries of the Solimões River.
FishBase lists a water temperature of 20 to 26°C and a pH of 5.0 to 7.0, that is, soft and acidic water. The map shows the three native countries; the fish lives only in suitable Amazonian streams within them. Captive-bred neon tetras are kept in aquariums all over the world, but those are pets, not wild populations.
Continent
Its habitat
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Clear and blackwater forest streams of the western Amazon basin, including tributaries of the Solimões River. The fish lives only in suitable streams within each country shown; aquarium fish elsewhere are pets, not wild populations.
Places: Brazil, Colombia and Peru.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Colombia, Brazil, Peru, Venezuela and South Africa.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
What it eats
Neon tetras eat tiny food.
They eat little worms, small bugs and tiny water animals. They also nibble bits of plants.
Neon tetras are omnivores, which means they eat both animals and plants. Grown-up neon tetras eat worms, small insects and crustaceans (tiny relatives of shrimp and crabs), as well as bits of plants.
Everything they eat has to be very small, because their mouths are tiny. In aquariums, fish breeders feed them foods such as bloodworms and tiny water fleas.
FishBase reports that adults feed on worms, small insects, crustaceans and plant matter, making the species an omnivore of small prey. Details of its wild diet in particular streams have not been described in the sources used here.
In captive breeding, broodstock have been fed bloodworms, tubifex worms and cladocerans (water fleas) three times a day, at 4 percent of body weight, in a 2016 hatchery study by Kadtan and colleagues.
Did you know?
A neon tetra is about as long as a coin is wide.
A grown-up neon tetra is only about 2.5 centimeters long, not counting its tail.
Maximum standard length is 2.5 centimeters (FishBase), about the diameter of a US quarter.
A stripe made of light
The neon tetra's blue stripe is shiny, like a mirror.
It is made by tiny shiny plates in its skin. The stripe can change color when the light gets brighter or darker.
Most colors in animals come from pigments, colored chemicals like the ones in paint. The neon tetra's blue stripe is different. It is made by tiny, flat, mirror-like plates stacked inside special skin cells. When light bounces off the stacks, some colors get stronger and others cancel out, so the stripe shines.
Amazingly, the neon tetra can change its stripe's color when the light around it changes. Scientists think the little plates tilt, like the slats of a window blind, and in 2011 a team in Japan made careful measurements that supported this idea.
The stripe is a structural color: iridophores contain a few stacks of periodically arranged, light-reflecting platelets that cause multilayer optical interference. Unlike the structural colors of butterfly wings and bird feathers, the neon tetra's can change with the light intensity of its surroundings.
The proposed explanation is the "Venetian blind" model: the platelets tilt during a color change, altering the spacing between them and therefore the wavelengths reflected. Yoshioka and colleagues (2011) measured the spectrum and direction of light reflected by a single platelet stack and found that their results quantitatively verified this model.
Growing up
Neon tetras hatch from very tiny eggs.
The babies hatch in about one day. People who raise neon tetras keep the eggs in warm water.
Neon tetras lay eggs. Most of what is known about their eggs comes from fish raised in tanks. In tanks, a female lays a fairly small number of eggs, and they hatch in about one day.
Warmth speeds things up. In one hatchery study, eggs hatched in 24 to 26 hours at 26°C, but took 38 to 40 hours at a chilly 18°C. The warmer eggs also hatched better.
The life cycle described in the sources is from captivity. FishBase notes that in tanks the female lays a relatively small number of eggs, which hatch in about 24 hours.
Kadtan and colleagues (2016) incubated artificially fertilized eggs from cultured broodstock at 18 to 26°C. Incubation time fell as temperature rose, from 38 to 40 hours at 18°C to 24 to 26 hours at 26°C, and mean hatching success rose from 52.2 percent at 18°C to 70 percent at 26°C. They recommended 24 to 26°C for hatchery propagation and larval rearing. How neon tetras spawn in wild Amazonian streams, and how long they live there, are not described in the sources used here.
Living lights in dark water
Neon tetras live in streams that can be dark.
Their shiny stripes catch the light. In aquariums, people keep them together in a group.
Neon tetras live in forest streams, some with clear water and some with dark water. Their shiny stripes catch whatever light gets through, and they can change their stripe's color as the light changes.
In aquariums, experts recommend keeping neon tetras in groups of five or more in a tank at least 60 centimeters long. Scientists still have not worked out whether wild neon tetras migrate.
Little is published about the wild behavior of P. innesi; FishBase records its migratory behavior as undetermined. What is well documented is its ability to adjust the color of its iridescent stripe as ambient light changes.
For captive fish, FishBase's aquarium guidance is a group of at least five individuals in a tank at least 60 centimeters long, in soft, acidic water at 20 to 26°C, the conditions FishBase lists for the species.
Did you know?
Most pet neon tetras are born on fish farms.
The IUCN reports that most neon tetras in the aquarium trade are bred in Asia, and fewer than 5 percent are caught in the wild.
Citing Chapman and colleagues (1998), the IUCN assessment reports that under 5 percent of aquarium neon tetras were wild-caught, the rest captive-bred in Asia.
Wild streams and the aquarium trade
Wild neon tetras are doing well.
Their forest streams are in good shape. Almost all pet neon tetras are raised on fish farms, not caught in the wild.
The IUCN lists the neon tetra as Least Concern, and says its wild population seems to be stable. It lives across a wide area of forest streams that are still in good condition.
Neon tetras are hugely popular pets. But the IUCN reports that most neon tetras in the aquarium trade are bred in captivity in Asia, with fewer than 5 percent caught in the wild, so collecting for pets is probably not a serious threat.
The IUCN assessed P. innesi as Least Concern on 4 March 2021 (published 2023), citing its broad, if somewhat localized, distribution across the western Amazon in well-preserved aquatic habitats, and a population thought to be stable. No conservation actions are reported.
The only obvious threat is harvest for the aquarium trade, which the assessment judges probably not intense enough to matter: citing Chapman and colleagues (1998), it reports that most aquarium neon tetras are captive-bred in Asia, with less than 5 percent wild-caught. Those figures are from the late 1990s.
IUCN Red List
How is the neon tetra doing in the wild?
- Least Concern (this animal)
- Near Threatened
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Least Concern
Not at risk of disappearing from the wild right now.
Amazing facts
-
The neon tetra's stripe can change color.
The neon tetra can change the color of its shining stripe when the light around it changes.
Unlike the fixed structural colors of butterfly wings and bird feathers, the neon tetra's structural color varies with ambient light intensity.
-
A neon tetra is about as long as a coin is wide.
A grown-up neon tetra is only about 2.5 centimeters long, not counting its tail.
Maximum standard length is 2.5 centimeters (FishBase), about the diameter of a US quarter.
-
Most pet neon tetras are born on fish farms.
The IUCN reports that most neon tetras in the aquarium trade are bred in Asia, and fewer than 5 percent are caught in the wild.
Citing Chapman and colleagues (1998), the IUCN assessment reports that under 5 percent of aquarium neon tetras were wild-caught, the rest captive-bred in Asia.
Words to know
- iridescent
- shining with colors that seem to change as the light or viewing angle changes
- structural color
- color made by tiny structures that bounce light, not by pigment
- blackwater
- stream or river water that is naturally dark brown, like tea
- omnivore
- an animal that eats both plants and animals
- captive-bred
- born and raised in the care of people, not in the wild
Discovery challenge
-
Where do wild neon tetras live?
Where do wild neon tetras live?
Which describes the neon tetra's native habitat?
- Forest streams in the Amazon
- The salty ocean
- Ponds in the Arctic
Show the answer
Forest streams in the Amazon
Wild neon tetras live in rainforest streams in South America.
They live in clear and dark-water forest streams of the western Amazon, in Brazil, Colombia and Peru.
Terra firme streams with clear or dark water in the western Amazon basin (IUCN).
-
What makes the neon tetra's blue stripe shine?
What makes the neon tetra's blue stripe shine?
What produces the neon tetra's iridescent stripe?
- Blue paint
- Tiny mirror-like plates in its skin
- A light bulb inside it
Show the answer
Tiny mirror-like plates in its skin
Tiny shiny plates in its skin make the stripe shine.
Stacks of tiny, mirror-like plates in special skin cells bounce light to make the color.
Stacks of reflecting platelets in iridophores create multilayer interference, a structural color.
-
Where do most pet neon tetras come from?
Where do most neon tetras in the aquarium trade come from?
According to the IUCN, how are most aquarium neon tetras supplied?
- Fish farms
- Caught in Amazon streams
- The ocean
Show the answer
Fish farms
Most pet neon tetras are raised on fish farms.
Most are bred in captivity in Asia; fewer than 5 percent are caught in the wild.
Most are captive-bred in Asia, with under 5 percent wild-caught (Chapman and colleagues, 1998, cited by the IUCN).
-
How big is a neon tetra?
About how long is a grown-up neon tetra, not counting its tail?
What is the neon tetra's maximum standard length?
- About as long as a school bus
- About 2.5 centimeters
- About 1 meter
Show the answer
About 2.5 centimeters
It is tiny: about as long as a coin is wide.
It grows to about 2.5 centimeters, about as long as a US quarter is wide.
FishBase gives a maximum standard length of 2.5 centimeters.
Places where you might see it
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Watch
Country
Peru
Peru is a country on the Pacific coast of South America. It has a dry desert coast, the high Andes mountains and the Amazon rainforest, and about 34 million people lived there in 2025, many of them in the capital, Lima.
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Watch
Country
Colombia
Colombia is in the northwest of South America, with coasts on both the Caribbean Sea and the Pacific Ocean. Three ranges of the Andes run through it, and most people live in the cool mountains, where the capital, Bogotá, sits on a high plateau. About 53.4 million people lived there in 2026, according to DANE, the national statistics office.
-
Watch
Country
Brazil
Brazil covers about half of South America and is the fifth-largest country in the world. It holds most of the Amazon River basin and much of the world's largest rainforest, and about 214 million people lived there in 2026, most of them near the Atlantic coast.
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Peru
Peru is a country on the Pacific coast of South America. It has a dry desert coast, the high Andes mountains and the Amazon rainforest, and about 34 million people lived there in 2025, many of them in the capital, Lima.
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Colombia
Colombia is in the northwest of South America, with coasts on both the Caribbean Sea and the Pacific Ocean. Three ranges of the Andes run through it, and most people live in the cool mountains, where the capital, Bogotá, sits on a high plateau. About 53.4 million people lived there in 2026, according to DANE, the national statistics office.
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Watch
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Brazil
Brazil covers about half of South America and is the fifth-largest country in the world. It holds most of the Amazon River basin and much of the world's largest rainforest, and about 214 million people lived there in 2026, most of them near the Atlantic coast.
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For parents & teachers
What children will learn
- Describe where wild neon tetras live and how that differs from pet neon tetras.
- Explain structural color and how the neon tetra's stripe can change.
- Understand why the IUCN considers the aquarium trade a small threat to this species.
- Recognize that some facts about an animal come only from captive studies.
Recommended ages: 3 to 17 · About 12 minutes
Talk about it
- Why might it be good for wild fish that most pet neon tetras are raised on farms?
- How could a stripe that changes color help a small fish in a dark stream? (Scientists are still finding out.)
- Why do scientists know more about neon tetra eggs in tanks than in the wild?
Try at home or in class
- Look at a CD or soap bubble under a lamp and tilt it: the colors you see are structural colors, like the neon tetra's stripe.
- Place a quarter on a ruler: a grown-up neon tetra is about that long.
Key vocabulary: iridescent, structural color, blackwater, omnivore, captive-bred
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Paracheirodon innesi, assessment 2023 , IUCN Red List of Threatened Species
- Paracheirodon innesi summary , FishBase
- Mechanism of variable structural colour in the neon tetra: quantitative evaluation of the Venetian blind model (Yoshioka et al., 2011) , Journal of the Royal Society Interface (PubMed abstract)
- Effect of temperature on incubation period and hatching success of neon tetra, Paracheirodon innesi eggs (Kadtan et al., 2016) , Journal of Indian Fisheries Association
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 27, 2026. Spotted a mistake? Tell us.