Least Rasbora (Boraras urophthalmoides)

Family: Cyprinidae

Least Rasbora — a Cyprinidae from Southeast Asia, peaceful, restless swimmers that use every inch. Reaches 3–4.4 cm; groups of 6 minimum; bigger schools calm them. 25–28 °C.

Care parameters

Water temperature
25–28 °C
pH
5–6.5
GH hardness
5–12 dGH
Adult length
3–4.4 cm
Minimum tank
25 L
Water layer
Bottom-dwelling
Difficulty
Moderate
Temperament
Peaceful, restless swimmers that use every inch
Origin
Southeast Asia

Species overview

Cyprinidae species Boraras urophthalmoides comes from Southeast Asia. A restless micropredator of the surface film, evolved for open, sunlit water. It lives on the bottom. Adults reach 3–4.4 cm. Groups of 6 minimum; bigger schools calm them. Generous swimming room, a big school and clean water cover nearly all of its care. Maintain 25–28 °C at pH 5–6.5. A solid choice for a well-planned community tank.

Native biotope

Habitat
Clear streams and rivers over gravel
Flow
Moderate, well-oxygenated current
Dissolved O₂
Appreciates well-oxygenated water

Aquascape & hardware

Substrate
Fine gravel and sand
Hardscape
Water-worn stones and driftwood
Plants
Hardy rooted plants along the margins

Temperament, diet & tankmates

Schooling
Groups of 6 minimum; bigger schools calm them
Diet
Small surface-oriented omnivore; flakes and tiny live foods
Recommended tankmates
  • Other danios and small rasboras — Form a fast, peaceful upper-water school
Avoid keeping with
  • Slow, timid fish — Outcompeted at the surface

Breeding & notes

Sexual dimorphism
Males often slimmer and more colourful
Breeding method
Typical egg-scattering minnow; mop spawning works