Least Rasbora (Boraras urophthalmoides)

Species Overview The Least Rasbora (Boraras urophthalmoides) is proof that some of the most captivating aquarium fish are also among the smallest. Rarely exceeding an inch in length, this peaceful nano species brings subtle beauty, constant movement, and fascinating schooling behavior to planted aquariums. Their delicate bronze-to-copper coloration and active nature make them a favorite among aquarists who appreciate natural aquarium displays over flashy showpieces. When maintained in proper groups, Least Rasboras spend much of their day moving together through plants and open water, creating a sense of life and activity that makes an aquarium feel truly established. Their small size allows them to utilize every corner of the aquarium without overwhelming the aquascape, making them particularly well suited for nano aquariums and carefully designed planted tanks. At Aquatic Arts, we especially appreciate Least Rasboras for their versatility and peaceful temperament. They are excellent community aquarium fish, pair well with many other nano species, and are among the best choices for hobbyists looking to build a thriving planted ecosystem. Whether you are setting up your first nano aquarium or expanding an established collection, the Least Rasbora offers a rewarding fishkeeping experience that proves size is not everything. What We Love About This Fish • One of the smallest aquarium fish available in the freshwater hobby • Peaceful schooling behavior that brings life to planted aquariums • Excellent choice for nano community aquariums • Generally compatible with established dwarf shrimp colonies Quick Care Guide • Care Level: Easy • Temperament: Peaceful schooling fish ideal for nano and planted aquariums • Diet: Omnivore that readily accepts prepared, frozen, and live foods • Source: Wild Caught • Average Adult Size: 0.75–1 inch (1.9–2.5 cm) • Average Purchase Size: 0.5–0.75 inch (1.3–1.9 cm) • Tank Level: Middle Water Column • Activity Level: Active Throughout the Day • Group Size: Schooling species; best maintained in a school of 6 or more • Shrimp Compatibility: Generally safe with adult shrimp; may consume shrimplets Tank Parameters • Recommended Tank Size: 5 Gallons or Larger • Temperature Range: 72–82°F (22–28°C) • pH Range: 5.5–7.5 • GH Range: 1–8 dGH • KH Range: 0–4 dKH • TDS Range: 50–200 ppm