The Danio genus belongs to the family Cyprinidae and comprises many of the species of danionins familiar to aquarists. The common name “danio” is used for members of the genera Danio and Devario – and the name ‘danio’ originates from the Bengali name dhani, meaning “of the rice field”.
They are native to the freshwater rivers and streams of Southeast Asia. Many species of this family are brightly coloured and are readily found in aquaria across the world. But many more have been and still are being discovered, and are waiting for scientific names.
Danios have two pairs of long barbels and are characteristically horizontally striped, except for the Glowlight, Panther and Black-barred Danios, which have vertical bars. They range from 4-15 cm in length. They generally do not live for more than two to three years, and are probably annual fish in the wild. In the wild, these fish consume various small aquatic insects, crustaceans and worms and they usually breed during the warm rainy season.
In the aquarium, Danios are primarily surface feeders and omnivores. While flake food is suitable, it should be varied with live or frozen foods, especially brine shrimp and blood worms. Since Danios are voracious feeders, particular care should be taken that timid tank mates do not starve! As most fish would, they also will eat any eggs produced in the tank, and they may feast on any fish small enough to fit in their mouths. Danios are naturally boisterous and may chase each other or other fish, or occasionally nip at fins. Nevertheless, they are not aggressive and will generally not attack others, thus they are good community tank fish. As a schooling fish, they prefer to be in groups of six or more.
Danios do best in longer aquariums with space enough to cater for their active swimming, preferably with current produced by a power filter, which helps emulate their natural habitat. They prefer water with a 6.0 to8.0 pH, a water hardness of 5-12 dGH, a carbon hardness of 6-12 KH and a temperature ranging between 18° and 24°C, the lower temperature being the more ideal.
Some species of Danio, such as the Zebra Danio, are easy to breed. They scatter their non-adhesive eggs over the substrate and plants and these thus perhaps inevitably become a food treat for others, unless protected by substrate, pebbles and rocks. Heavy substrate planting also helps. The fry hatch within 2 to 3 days. When conditioning Danios for breeding, it is advisable to feed them plenty of fresh foods, such as brine shrimp and bloodworms. Both females and males show a degree of colour changes during the spawning season, but more so the males.
Since Danios are considered hardy, they are a great choice for beginners and community tanks.