Dario dario is a small, but at first sight very attractive fish, originating from the waters of the Indian provinces of West Bengal and Assam. It makes its home in small streams in the Brahmaputra river basin.
The species was first caught and brought to Germany in the summer of 1999; already in January 2000, the first scientific description was published in the journal Het aquarium, authored by W. A. Tomey. In this description, the fish was introduced to the public as Badis badis bengalensis. Following a revision of the genus Badis in 2001, the species was separated and renamed Dario dario, thus creating the new genus Dario. This genus currently includes the taxa: dario, dayingensis, hysginon, sp. ‘Bangladesh’ and sp. ‘Aquarium Glaser 2004’. [1]
In nature, these fish live in slow-flowing, densely overgrown streams. Frank Schäfer (one of the successful hunters of this species in India) gives the following parameters of the site where the fish were caught: the stream had a maximum width of 5 metres and a depth of up to 70 centimetres. The total hardness of the water was 6 °dGH, the carbonate hardness was not indicative and the pH was around 6,4. In the crystal clear water, dense stands of Vallisneria sp. grew[1].
In an aquarium, keeping these fish is relatively easy if basic hygiene rules are followed. They are undemanding in terms of water composition, as long as we do not go to extremes, of course. A temperature range of 22 to 26 ˚C suits them. The breeding tank should be densely overgrown with a wide variety of plants, and a mini aquarium of 30 x 20 x 20 centimetres is sufficient for one pair. Various decorative items such as roots and stones should also be placed in the tank.
The male Dario dario fish differs significantly from the female in size, but especially in the very intense colouring of the body and fins. It grows to a size of 25 mm. Its colouration consists of a silvery-turquoise base with vertical red stripes. The pelvic fins are elongated compared to the female. The female is smaller, growing to a size of 22 mm. Her colouration is bland, silvery brown.
Males form territories of approximately 30 x 30 cm, which should be taken into account when setting up a tank. They guard their territories closely and any intruder is immediately driven beyond the territory boundaries upon sighting. Fights between rival males are mostly harmless and limited to displaying colouration and fins in a ‘ritual dance’. The weaker individual is expelled from the territory. The loser occasionally takes a torn fin from the fight in addition to the injury to his honour. However, if a dominant male clashes with a submissive individual, the latter may be constantly pursued and, in extreme cases, beaten to death.
The females move to the borders of the males’ territories, or in an undefended part of the tank, and try to escape the attention of the males. There are also mild exchanges between them, but only in the form of intimidation. Most of the day, however, the fish take no notice and devote themselves to foraging for food.
Dario dario only accept live food, which they hunt very actively, but in case of emergency they will also get used to some types of small frozen food. We can offer them cyclops, small daphnia, freshly hatched daphnia (artemia), micras, or grindal. The fish have some problems with live patent due to the size of the mouth, but in extreme cases it is also possible to feed it or cortara. I haven’t tried the threadfins yet. From my own experience, I know that dried and artificial foods will not touch the fish, even if it would cost them their lives.
Small, quiet fish, preferably surface dwelling species, can be placed as companions to the gifts. Personally, I recommend keeping them in monoculture, but I have also had good experience with keeping these fish together with Pseudepiplatys annulatus.
Rearing is already a bit more demanding. The key to success seems to be the use of peat liquor in the spawning water (which should be soft and slightly acidic) and feeding the floated spawn with swirls. During the spawning season the males are beautifully richly coloured and are constantly trying to lure females into their territory with a ‘wedding dance’. This is an interplay of undulating movements, displaying taut fins and colouration in close proximity to the female who, if ready to spawn, follows the male into his territory. There, the partners search for a suitable place to deposit their eggs.
The spawning act itself is very similar to that of Betta splendens. The male wraps himself around the female and, with gentle shaking by both partners, the sexual products are released. The fish remain in this rigid position for a few more seconds and, once they have reawakened, begin again to look for a new place to deposit their eggs. During one spawning act, the female releases an average of 1 to 3 eggs, which are glassy clear and slightly sticky. The eggs are very small, only 1 to 1,2 mm in size.
The tiny, roughly 2 mm long fry hatches from the eggs in 24 to 36 hours, depending on the temperature, and after hatching lies on the bottom or hangs on the walls of the tank. Hatching of the fry occurs 72 hours after hatching. At this stage, the young fish still have some reserves in the yolk sac, so that the first food intake does not take place for another 24 hours or so. This is where the biggest problem occurs. Due to their size, the fish are only able to consume the finest “dusty” live food. The most suitable first food is whirligigs, e.g. Blepharisma japonica, or possibly other species. In my experience, the fish are also able to consume Paramecium funnelworm, but in this case there is a relatively large loss and the growth of the spawn is slower. After the juveniles have switched to Artemia nauplii, which is about a week after spawning (to be tested), further rearing is basically identical to broodstock rearing of other spawning fish species.
The fry start to color at about 1.5 cm, become sexually mature at about 2 cm at 4 to 5 months of age, and begin the cycle of life again.
I personally use a 70 x 30 x 30 cm tank for rearing, where I place a spawning grate over part of the bottom. I separate this part from the rest of the tank with a glass partition. Above the grate I place a coconut shell and a clump of Java moss. In the second part of the tank I place a fairly large number of fine-leaved plants, which serve to cultivate small organisms that later act as food for the spawn. The bottom of the tank is bare. The fish spawn above the grate in the Java moss and the released eggs fall to the bottom below the grate. After 2 days of spawning, I catch the adult fish, remove the glass baffle and grate from the tank and let the young fish scatter all over the tank. Next comes the development of the fry as mentioned above.
[1] http://nothobranchius.de/html/zwergblaubarsche.html