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EveryFish
A leopard danio (danio rerio) in a home aquarium

Zebrafish

Small striped fish from South Asia kept in aquariums and labs

Photo: Roundish, CC0, via Wikimedia Commons

The zebrafish is a small striped fish native to freshwater habitats in South Asia. It is kept in home aquariums for its hardiness and quick breeding while serving as a model organism in developmental biology and genetics because its embryos are transparent and grow fast outside the mother.

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  • Grows to a maximum of 5 cm long
  • Transparent embryos develop outside the mother
  • Can regenerate heart and fin tissue
  • First species sold as fluorescent GloFish
  • Used to study vertebrate development and gene function

What it is

The zebrafish belongs to the carp family and has a slim body flattened from the sides. Five blue stripes run along each side from head to tail fin. Males show gold between the stripes and a pointed shape while females have a rounder body with silver stripes and a pale belly. They reach up to 5 cm long. These fish live in shallow fresh waters with some plants along the banks.

Where it lives

This species occurs in freshwater across South Asia, mainly in the Ganges and Brahmaputra river systems. Records exist from India, Pakistan, Bangladesh, Nepal and Bhutan, with the northern limit near the Himalayas. They occupy streams, canals, ditches, ponds and rice fields that have clear water and some vegetation. Water temperatures in these places mostly range from 16.5 to 34 degrees Celsius.

How it lives

Zebrafish swim in groups of six or more and get along with other fish in tanks. They can regrow parts of the heart and fins after injury. In laboratories they have been used to examine many processes including how cells repair tissue and how genes work during growth.

Breeding and life cycle

These fish spawn often when conditions are right, with females producing hundreds of eggs every two or three days. A male must be present for spawning. The eggs are clear and begin developing right away, with major organs forming within 36 hours. Young reach adult size in a few months. Plants in the tank encourage the process.

Zebrafish
A drawing made by EveryFish from what this page says. It is a diagram, not a picture of the real fish.

Fish and people

Zebrafish are sold as beginner aquarium fish because they are tough and breed readily. They were the first species turned into fluorescent GloFish for the pet trade. In laboratories they are a standard model for studies of development, gene function, toxicology and tissue repair. Their clear young make it simple to watch growth and test substances in the water.

A Zebrafish Pigment Mutant. The mutant called bleached blond was produced by insertional mutagenesis. The embryos in the picture are four days old. At the top is a wild-type embryo, below is the mutant. The mutant lacks
A Zebrafish Pigment Mutant. The mutant called bleached blond was produced by insertional mutagenesis. The embryos in the. Photo: Adam Amsterdam, Massachusetts Institute of Technology, Boston, Massach, CC BY 2.5, via Wikimedia Commons
Zebrafish, like humans, have a backbone and many genes in common with humans. In one laboratory test, the addition of the chemical ketamine—a pediatric anesthetic—lowers the fish’s heart rate and reduces the number of ne
Zebrafish, like humans, have a backbone and many genes in common with humans. In one laboratory test, the addition of th. Photo: The U.S. Food and Drug Administration, Public domain, via Wikimedia Commons
Danio rerio (Zebrafish) 6 days post fertilization treated with 10 µL of 1,4 Dioxane
Danio rerio (Zebrafish) 6 days post fertilization treated with 10 µL of 1,4 Dioxane. Photo: Tarabehmanesh, CC BY 4.0, via Wikimedia Commons

Questions people ask about Zebrafish

Where does the zebrafish live?

It is native to freshwater habitats in India, Pakistan, Bangladesh, Nepal and Bhutan, mainly in the Ganges and Brahmaputra river basins.

Why is it used in research?

Its embryos are transparent, develop quickly and can be produced in large numbers, making it easy to study development and test drugs.

How long does it live?

In captivity zebrafish live around two to three years, though some reach over five years in good conditions.

How does it reproduce?

Females lay hundreds of eggs every few days when a male is present, and the clear eggs start developing right away.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Zebrafish", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

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Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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