Harlequin Rasbora

The Harlequin Rasbora (Trigonostigma heteromorpha) is a small, vibrant freshwater fish prized for its shimmering copper-orange body and distinct black triangular marking. Native to Southeast Asia, particularly Thailand, Malaysia, and Sumatra, this peaceful schooling fish is ideal for community aquariums.

Tank Size:
A minimum of 10 gallons is required for a small school, but a 20-gallon tank or larger is ideal for a more natural schooling behavior.

Substrate & Decorations:
Harlequin Rasboras thrive in planted tanks with dark substrates that mimic their natural blackwater habitats. They appreciate:

• Live plants (Java Fern, Anubias, Cryptocoryne)
• Driftwood and leaf litter for natural tannins
• Dim lighting or floating plants to diffuse light

Filtration & Water Flow:
A gentle filtration system is recommended, such as a sponge filter or a low-flow hang-on-back filter. They are accustomed to slow-moving waters and can be stressed by excessive currents.

Behavior and Compatibility:

Growing to about 1.75 inches (4.5 cm) in length, Harlequin Rasboras are best kept in groups of six or more to encourage natural schooling behavior and reduce stress. They are omnivores, accepting a varied diet of high-quality flakes, pellets, and live or frozen foods such as daphnia and bloodworms. Their hardy nature and vibrant coloration make them an excellent choice for community tanks, where they coexist well with similarly peaceful species. Ideal water parameters include a temperature range of 72-80°F (22-27°C), pH between 6.0 and 7.5, and a soft to moderate hardness level. Providing a well-structured environment with plenty of swimming space, dim lighting, and dark substrate enhances their colors and natural behavior.