danios

Danios are small, active freshwater fish in the genus Danio, part of the family Cyprinidae. They are popular in home aquariums and include several well-known species, among them the zebra danio (Danio rerio), which has become a major model organism in scientific research due to its rapid development and transparent embryos.

Habitat and distribution

Danios are native to South Asia and parts of Southeast Asia, including streams and rivers in India, Bangladesh, Nepal, Myanmar, and nearby regions. They inhabit clean, well-oxygenated waters with moderate currents and can tolerate a range of tropical temperatures. In the aquarium trade, danios are widely kept and bred.

Description

Most Danio species are small, typically about 2–5 cm in length, with coloration that often includes horizontal stripes, iridescent markings, or metallic hues. The zebra danio, one of the most familiar, features three to four blue-silver stripes along a light body. Species vary in pattern and size, and hybrids or regional varieties are common in captivity.

Behavior and care

Danios are peaceful, schooling fish that do best in groups. They require a well-filtered, aerated aquarium with moderate to strong water movement. Water conditions are generally forgiving: temperatures around 22–28°C, pH near neutral, and regular maintenance of water quality. They are omnivorous, feeding on flake foods, live/frozen foods, and small invertebrates.

Reproduction and use

In breeding, danios are egg scatterers that lay adhesive eggs among plants or substrate. Breeding triggers include changes in light and temperature. Danio rerio has become a widely used model organism in genetics and developmental biology due to its rapid growth, transparent embryos, and sequenced genome.

Conservation and taxonomy

There are several recognized Danio species, most with a broad geographic range and stable populations in the wild, though habitat degradation can affect local populations.