Least Rasbora (Boraras urophthalmoides)

Least Rasbora Boraras urophthalmoides
Name	Least Rasbora
Name Lat.	Boraras urophthalmoides
Synonym	Rasbora urophthalmoides
Family	Danios
Family lat.	Danionidae
Order	Carps
Order lat.	Cypriniformes
Origin	Southeast Asia
Habitat	Forest streams, ponds
Diet	Carnivore
pH	6.0-7.0
Behavior	Peaceful
Keeping	Swarm
Care Level	Difficult
Reproduction	Egg scatterer
Breeding	Difficult
Life Span	2-4 years
Protection	No
Metric Units
Size	2 cm
Temperature	24-28 °C
Hardness	1-10 °dH
Aquarium	60 cm / 54 l
US Units
Size	0.8"
Temperature	75-82 °F
Hardness	18-178 ppm
Aquarium	15 gal

Distribution and habitat

The distribution range of the tail-spotted danios extends from southern Thailand across the Malay Peninsula to eastern Sumatra. There they live in weedy ponds, pools, rice fields and floodplains as well as in slow-flowing forest streams with dense plant growth, fallen leaves and twigs.

Maintenance

The aquarium should have a dense border planting, with hiding and retreat possibilities (roots, stones) and offer sufficient swimming space. In soft, slightly acidic water, subdued light (floating plants) and a dark substrate covered with some foliage (e.g. sea almond leaves) they show the most beautiful coloration.

No ammonia, ammonium and nitrite should be detectable, the nitrate value should not exceed 100 mg/l. To ensure the water quality and oxygen content, a filter and heater adapted to the aquarium size is required, as well as lighting for the species-appropriate day-night rhythm of the animals.

Diet

In the wild they feed on insect larvae, small crustaceans, worms and other zooplankton. The diet consists of small live foods such as daphnia, cyclops, artemia, mysis and mosquito larvae, which are also well accepted frozen, plus commercially available frozen special food mixtures, supplemented with a high-quality, protein-rich dry food (granules, flakes, micropellets). Regular and varied feeding promotes good health. Only as much should be fed as is eaten immediately (in a maximum of 10 minutes).

Behaviour and compatibility

These very peaceful and shy schooling fish are not suitable for a community tank due to their small size. Ideal is the keeping in a species tank or together with other small fish species, like Microdevario, Sundadanio, Trigonostigma etc.. Always a group of at least 8 animals, but better more should be kept together. Basically, only compatible fish species with similar requirements to the water condition and water temperature may be socialized.

Sex dimorphism

The males are slimmer, smaller and more intensely colored than the more round-bellied females.

Reproduction and breeding

They are free spawners and spawn predators. The female spawns between fine-feathered plants (Java moss) near the bottom. The larvae hatch after 18-48 hours and swim freely after 1-2 days.

Fry must be fed several times a day with special rearing food (Artemia nauplii, microworms, dust food). In a community tank breeding is hardly possible, because the spawn is easy prey.

Important

The foliage (sea almond tree, oak, etc.) not only provides cover, it enriches the water with humic substances, naturally lowers the pH and, as it rots, promotes the development of microorganisms that provide a valuable secondary food source.

The well-being of the fish should be monitored regularly. Temperature should be checked daily, pH, hardness and nitrate levels at least every 14 days. Regular partial water changes are recommended, even when contaminant levels have not yet reached the upper limit. Sudden changes in water quality should be avoided. Newly introduced fish must be accustomed slowly to the water in the aquarium.

Further literature can be found in your pet store.

References

Text: Werner Winter; Image: petdata

Source: BMELV (1998): Tierschutzgutachten - Haltung von Zierfischen (Süßwasser); ENGELMANN (2005): Zootierhaltung - Tiere in menschlicher Obhut: Fische, Verlag Harri Deutsch

• Gemäß § 21 Abs. 5 Tierschutzgesetz idgF