Harlequin Rasbora (Trigonostigma heteromorpha)

Origin and Habitat:
The Harlequin Rasbora, scientifically named Trigonostigma heteromorpha, is native to Southeast Asia. It is primarily found in the slow-moving, soft, and acidic waters of Thailand, Malaysia, and Singapore. These regions are home to blackwater streams and peat swamps, which are rich in organic material that gives the water its characteristic brown tint. Harlequin Rasboras are accustomed to densely vegetated habitats, where they swim in schools, foraging for food among the plants.

Appearance:
Harlequin Rasboras are easily identified by the distinct black, triangular-shaped patch on the rear half of their bodies. Their name “Harlequin” refers to the resemblance of this marking to the pattern on the traditional harlequin costume. These fish have a bright, metallic copper or reddish-orange body, with the contrasting black patch adding to their striking appearance. They grow to about 1.75 inches (4.5 cm), making them a small but vibrant addition to aquariums.

Aquarium Care:
Harlequin Rasboras are hardy, peaceful fish that are ideal for community tanks and beginner aquarists. They are schooling fish that do best when kept in groups, which allows them to exhibit their natural behaviors.

• Tank Size: A minimum of 10 gallons is recommended for a small group of 6 Harlequin Rasboras, but larger tanks (20 gallons or more) are better if keeping a larger school. The more space they have, the more comfortable and active they will be.
• Water Parameters: These fish prefer warm, soft, and slightly acidic water, with a temperature range of 72°F to 81°F (22°C to 27°C) and a pH level between 6.0 and 7.5. While they are adaptable, maintaining stable water parameters and good filtration is key to their health. A tank with a gentle current and soft water conditions is ideal.
• Diet: Harlequin Rasboras are omnivores and thrive on a varied diet. High-quality flakes, micro-pellets, and frozen or live foods such as daphnia, bloodworms, and brine shrimp are excellent choices. Providing a balanced diet with both protein-rich foods and plant matter helps maintain their vibrant coloration and overall health.
• Behavior and Temperament: Harlequin Rasboras are peaceful, schooling fish that should be kept in groups of at least six to eight individuals. In larger schools, they become more active and confident, swimming together in tight formations. They make excellent tank mates for other small, non-aggressive species like tetras, guppies, or small catfish. Avoid housing them with larger or aggressive fish that might view them as prey.

Aquarium Setup:
To mimic the natural habitat of Harlequin Rasboras, it’s important to provide plenty of plants, driftwood, and other decorations that offer hiding spots and create a sense of security. Live plants like Java fern, Anubias, and floating plants work well, as they replicate the shaded, forest-like environment these fish are accustomed to. Additionally, a dark substrate can help highlight their vibrant colors. While they can adapt to brighter lighting, using dim or diffuse lighting through plants helps create a more natural and comfortable environment.

Breeding:
Breeding Harlequin Rasboras is possible in a home aquarium, although it requires slightly acidic, soft water and a well-planted tank. During courtship, males display their best colors and attempt to attract females by swimming in an arching motion. Once the female lays her eggs, they are typically deposited on the underside of broad plant leaves. The adults do not care for the eggs, so it's important to remove them to prevent predation by the parents or other fish. The eggs will hatch in about 24 hours, and the fry can be fed infusoria or finely crushed flake food once they are free-swimming.

Lifespan:
With proper care, Harlequin Rasboras can live up to 5 to 8 years in captivity. Ensuring stable water conditions and a healthy, varied diet is essential for their longevity.

Conclusion:
Harlequin Rasboras are a stunning, peaceful species that bring both color and activity to any freshwater aquarium. Their striking appearance, coupled with their peaceful nature, makes them an excellent choice for community tanks. Whether you’re a beginner or a seasoned aquarist, Harlequin Rasboras are a hardy, easy-to-care-for species that can thrive in a well-planted, peaceful environment.