The Least Rasbora (Boraras urophthalmoides) is one of the smallest and most charming freshwater fish available for nano aquariums. Native to the blackwater streams and peat swamps of Southeast Asia, this micro-rasbora is prized for its vivid red coloration, black eye-spot marking near the tail, and peaceful, social behavior.
Growing to only about 0.7–0.8 inches (2 cm) in length, the Least Rasbora is perfect for nano tanks, heavily planted aquascapes, and blackwater biotopes. They do best in groups of 8 or more, displaying natural schooling behavior that enhances both their well-being and the visual appeal of the tank.
- Scientific Name: Boraras urophthalmoides
- Common Name: Least Rasbora
- Max Size: ~0.8 inches (2 cm)
- Temperament: Peaceful, social
- Tank Size: Minimum 5 gallons
Ideal Water Parameters:
- Temperature: 72–82°F (22–28°C)
- pH: 5.5–7.0
- Soft, slightly acidic water preferred
Diet: Micro-pellets, crushed flakes, baby brine shrimp, daphnia, and other fine live/frozen foods
Why Choose the Least Rasbora?
- Perfect for nano and desktop aquariums
- Ideal for peaceful community tanks
- Thrives in blackwater and low-light environments
- Stunning coloration in mature planted tanks
- Low bioload and beginner-friendly care
Whether you're building a Southeast Asian biotope, a small aquascape, or simply want an active, colorful microfish, Boraras urophthalmoides is a top pick for aquarists looking for beauty in miniature. Add a school of these tiny jewels to your tank and watch them bring life and motion to every corner.