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Rainbow Tetra

Nematobrycon lacortei

SpeciesShort profile

From South America: the Río San Juan system of western Colombia, especially the Río Calima headwaters in Valle del Cauca123

At a glance the quick version

Length3.6 cm123
Sizesmall
Vivid shifting colours
Red-eyed males with long fins
Fits a calm community tank
2

Looks how to spot one

Slim characin (tetra) without an adipose fin, with filament-like tail rays

A slim tetra that, like its cousin the emperor tetra, has a three-lobed tail with thread-like rays. Males have bright red eyes, longer fins and vivid iridescent colours, while females have blue-green eyes and a fuller body.2

Coloursiridescent multi-coloured bodyred eyes in malesblue-green eyes in females2

Personality what they are like

Generally peaceful, though adult males claim small territories and spar with each other. In a mixed group with plenty of plants and cover this behaviour stays harmless and shows off their colours.21

Daily activity how busy a day looks

Moderately active; it prefers calm water with little current and enjoys exploring among plants and wood.2

Grooming and care the hands-on bits

Easy to look after in soft, clean water. Soft substrate, wood and live plants help it show its natural colours.21

Home where they are happiest

Tank of at least 120 x 30 x 30 cm (about 108 litres). Water 20-28 °C (FishBase gives 23-27 °C), pH 5.0-7.2, hardness 1-10 dGH. A blackwater-style setup with plants and wood suits it.21

Food basics what goes in the bowl

Probably an opportunistic omnivore in the wild. It takes good dried foods and thrives with regular small live or frozen foods such as bloodworm, Daphnia and brine shrimp.21

Company who they like around

Keep a mixed-sex group of at least 8-10. Good with similar-sized characins, catfish and non-predatory cichlids.21

The story where it all began

Weitzman and Fink described the rainbow tetra in 1971 and named it after Rosario LaCorte, an American aquarist and collector. It is one of only two species in the genus Nematobrycon, both found only in western Colombia.213

Fun facts for the dinner table

  1. 1

    It is named after the American aquarist Rosario LaCorte.1

  2. 2

    Nematobrycon is one of only two species in its genus, alongside the emperor tetra.2

  3. 3

    Males have red eyes and females blue-green eyes, so the sexes are easy to tell apart.2

  4. 4

    The genus name refers to the thread-like rays of its tail fin.2

Recognised by the official bits

IUCN Red List
Data Deficient (assessed 9 October 2014)1
FishBase
Used commercially in the aquarium trade1

The care rhythm a typical week and year

A typical home-care rhythm for a Rainbow Tetra. A starting point, not a vet's advice.

Owner questions the things everyone asks

How often should I feed my Rainbow Tetra?

Feed small amounts once or twice a day. Furry Diary's starting plan is to offer food daily, and it's best to give only what they can eat in a couple of minutes.21 Pet Wiki plan

What does a Rainbow Tetra eat, and what should it never eat?

They are omnivores and enjoy good dried foods plus regular small live or frozen foods like bloodworm, daphnia, and brine shrimp. Never feed anything that could foul the water or is not meant for fish; for specific restrictions, ask your vet or a good breeder.21

How much space does a Rainbow Tetra need?

A tank of at least 120 x 30 x 30 cm (about 108 litres) is recommended. This gives them room to swim and explore among plants and wood.21

What temperature, light or water does a Rainbow Tetra need?

Keep water temperature between 20-28°C (ideally 23-27°C), pH 5.0-7.2, and hardness 1-10 dGH. A blackwater-style setup with plants and wood suits them, and they prefer calm water with little current.21

How often should I clean a Rainbow Tetra's home?

Furry Diary's starting plan suggests a weekly 25% water change, weekly glass cleaning, and a monthly filter rinse in old tank water (never tap water). Also test the water weekly to keep it clean and soft. Pet Wiki plan

Can a Rainbow Tetra live with others?

Yes, they are generally peaceful and do best in a mixed-sex group of at least 8-10. They can live with similar-sized characins, catfish, and non-predatory cichlids.21

How long does a Rainbow Tetra live?

Their lifespan varies depending on care and environment. For a more precise estimate, ask your vet or a good breeder.

Can I handle a Rainbow Tetra?

It's best not to handle them as they are delicate fish. They are happiest when left to swim and explore in their tank.2

Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.

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Emperor TetraRoyal TetraDiamond Tetra

Where this comes from

Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.

  1. FishBase species summary: Nematobrycon lacortei fishbase.seused for describer, maximum length, distribution, water range, IUCN status
  2. Seriously Fish species profile: Nematobrycon lacortei seriouslyfish.comused for aquarium care, water parameters, behaviour, diet, sexing, habitat
  3. Wikipedia: Nematobrycon lacortei en.wikipedia.orgused for taxonomy history, etymology, appearance

Checked 2026-09-30. Text is written in our own words from these sources.