Harlequin Rasbora
Also known as: Trigonostigma heteromorpha
The Harlequin Rasbora is a small, vibrant freshwater fish known for its distinctive black triangular patch on the rear half of its body, contrasting with a coppery-orange base color. The Harlequin Rasbora originates from Southeast Asia, specifically Thailand, Malaysia, Singapore, and the Greater Sunda Islands (Sumatra and Borneo), reaches Adult size: 4.5 cm in captivity, typically lives 5-8 years, and is kept at 22-28°C (72-82°F). Individual fish vary, so treat this as a general guide rather than a guarantee.
Key facts
- Lifespan: 5-8 years.
- Adult size: Adult size: 4.5 cm (1.8 inches).
- Temperament: Peaceful, schooling fish; highly social and non-aggressive.
- Minimum tank: Minimum 60 liters (16 gallons) for a group of 6-8 individuals.
- Water temperature: 22-28°C (72-82°F).
- pH range: 6.0-7.5.
Species at a glance
- Origin
- Southeast Asia, specifically Thailand, Malaysia, Singapore, and the Greater Sunda Islands (Sumatra and Borneo)
- Adult size
- Adult size: 4.5 cm (1.8 inches)
- Life span
- 5-8 years
- Temperament
- Peaceful, schooling fish; highly social and non-aggressive
- Tank size
- Minimum 60 liters (16 gallons) for a group of 6-8 individuals
- Water temp
- 22-28°C (72-82°F)
- pH range
- 6.0-7.5
- Diet
- Omnivorous; accepts high-quality flakes, micro pellets, and live/frozen foods such as brine shrimp, daphnia, and bloodworms
- Other names
- Trigonostigma heteromorpha
About the Harlequin Rasbora
The Harlequin Rasbora is a small, vibrant freshwater fish known for its distinctive black triangular patch on the rear half of its body, contrasting with a coppery-orange base color. Native to slow-moving, shaded forest streams and peat swamps, it thrives in soft, slightly acidic water with dense vegetation. It is a classic community tank species due to its peaceful nature and striking appearance when kept in schools. Harlequin Rasboras are active swimmers that prefer the middle to upper water layers and exhibit natural schooling behavior in groups of six or more.
Lifespan and health
With optimal care, Harlequin Rasboras typically live 5-8 years, though exceptional specimens may reach up to 10 years in pristine conditions; longevity is strongly influenced by water quality, diet consistency, and stress reduction from adequate schooling numbers (minimum 6, ideally 8-10). Common health issues include ich (white spot disease) from temperature fluctuations or poor water quality, fin nipping if kept with aggressive tankmates, and bacterial infections stemming from organic waste buildup; preventative measures include quarantining new fish, maintaining stable parameters, and avoiding overcrowding.
Overview
The Harlequin Rasbora is a small, vibrant freshwater fish known for its distinctive black triangular patch on the rear half of its body, contrasting with a coppery-orange base color. Native to slow-moving, shaded forest streams and peat swamps, it thrives in soft, slightly acidic water with dense vegetation. It is a classic community tank species due to its peaceful nature and striking appearance when kept in schools. Harlequin Rasboras are active swimmers that prefer the middle to upper water layers and exhibit natural schooling behavior in groups of six or more.
Care and tank setup
Tank setup should include a densely planted aquarium with driftwood, leaf litter, and subdued lighting to mimic their natural blackwater habitat; use fine gravel or sand substrate and provide open swimming areas alongside plant cover. Maintain water parameters with a gentle flow from a sponge filter or low-output canister filter; perform 25% weekly water changes to keep nitrates below 20 ppm and ensure stable pH and temperature. Feed small amounts 2-3 times daily, offering only what they can consume within 2-3 minutes to avoid overfeeding and water quality degradation.
Sources
Related breeds
Breed information on this page is based on the Wikipedia article on the Harlequin Rasbora, supplemented with additional research. Reviewed for accuracy.