Taxonomy
The name Danio comes from the Bengali name dhani, meaning "of the rice field". The species Danio rerio was first described in the early 1800s by Francis Hamilton, a surgeon working for the British East India Company. About a century later, (1916) the genus was split; Danio being composed of the larger species and the new Brachydanio being composed of the smaller species, such as D. rerio. However, in 1991 the two genera were recombined; most larger species that were formerly within the Danio genus such as the giant danio have now been reclassified into the Devario genus. Also, Brachydanio now a junior synonym of Danio.
Characteristics
They are native to the fresh water rivers and streams of southeast Asia, but many species are brightly colored, and are available as aquarium fish worldwide. A number of the species have only been recently discovered, in remote inland areas of Myanmar and do not yet have scientific names.
They have two pairs of long barbels and are generally characterised by horizontal stripes (with the exception of the glowlight danio, panther danio and black barred danio which have vertical bars). They range from 4 cm/ 1.75 in) to 15 cm/ 6 in) 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 as well as in the case of fry and plankton.
In the aquarium
The care of members of the genus Danio are rather similar and easily generalized. They are easy to keep.
All of these fish are primarily surface feeders. They are omnivorous in the aquarium and will accept a wide variety of foods, though flake food is appropriate. Living in aquaria, live/frozen flaked foods are suitable, especially brine shrimp and sinking tablets. Danios are voracious eaters; take care so that timid feeders do not starve in community tanks with danios. When conditioning Danios for breeding, it's advisable to feed them plenty of fresh foods.
Although boisterous and liable to chase each other and other fish, they are good community fish and will not generally attack each other or other fish, although they occasionally nip fins, more by accident than design and will, like most fish, eat eggs and any fish small enough to fit into their mouths.
They are best kept in a tank long enough for their active swimming, preferably with a current from a power filter (or at least airstone) as they often live in fast flowing streams in the wild. Generally this also results in them being sub tropical with cooler temperatures. They are good jumpers and a tight fitting lid is recommended
Schooling fish, they prefer to be in groups of six or more. Danios prefer water with a 6.0–8.0 pH, a water hardness of up to 5.0–19.0 dGH,a carbon hardness of 8 to 12 KH, and a temperature range of 68–80 °F (18–24 °C), the lower end of the temperature range is ideal.
Breeding
Some species of Danios, such as the zebra danio are among the easiest aquarium fish to breed. Other species such as Danio kyathit are far harder to spawn. All scatter their eggs over the substrate. The eggs are non adhesive and hatch within 2–3 days. Eggs will be eaten enthusiastically unless protected by a layer of marbles or heavy substrate planting.
Hybrids between the Brachydanios species have been bred and the youngs can be raised to maturity but they are sterile.
