Chili Rasbora (Boraras brigittae)

Boraras brigittae, the Chili Rasbora (also Mosquito Rasbora), is one of the most sought-after micro-cyprinids for the planted nano aquarium hobby. Native to the blackwater peat swamps and forest streams of southern Borneo (Kalimantan, Indonesia), it is perfectly adapted to the extremely soft, highly acidic, tannin-stained waters of Southeast Asian peat environments.

At just 2 cm adult size, the Chili Rasbora is tiny — but what it lacks in size it makes up for in colour intensity. Males display a vivid cherry-red to chili-pepper red lateral stripe running from snout to tail, bordered above by a dark blue-black line. The body is pale pink to translucent, and the fins have red and black markings. Females are plainer and slightly larger.

In groups of 15–20 or more in a densely planted nano aquarium with dark substrate and tannin-stained water, Chili Rasboras create one of the most beautiful spectacles in the planted tank hobby — a shimmering cloud of red and black that contrasts dramatically with green and brown planting.

Boraras brigittae is closely related to Boraras urophthalmoides, from which it can be distinguished by the presence of a lateral stripe (brigittae) rather than just a lateral spot (urophthalmoides). Both species are sometimes sold under the same common names, creating occasional confusion in the hobby.

Tank Setup: A 20–40 litre nano planted aquarium. Dark, fine substrate (ADA Amazonia or similar), dense planting (Java moss, Rotala, Blyxa, Microsorum), Indian almond or catappa leaves for tannins, and a gentle sponge filter. Very low water flow — replicate near-still peat swamp conditions. The aquarium should be heavily established before adding Chili Rasboras.

Water Parameters: Temperature 23–28°C; pH 4.0–6.5; GH 1–5 °dH; KH 0–3 °dH. Very soft, acidic water is essential for vivid colour and long-term health. Use RO or rain water with a small amount of Indian almond extract or peat. Hard, alkaline water causes colour loss and health decline.

Feeding: Micro-omnivore. Feed baby brine shrimp, micro worms, Daphnia nauplii, powdered fry food, and crushed micro flake. Mouths are extremely small — all food must be micro-sized. Feed twice daily.

Tank Mates: Only the smallest, most peaceful species: other Boraras, Nano tetras (Ember Tetra), Pygmy Corydoras (if water chemistry is compatible), and peaceful dwarf shrimp. Avoid any fish 3 cm+. Neocaridina shrimp (Cherry Shrimp) may not thrive in the same very soft, acidic water conditions.

Behaviour: Loose schooling. Groups of 15+ are most impressive. Males display vivid colours in competition. Extremely peaceful toward all species.

Health: Sensitive to water quality, chemistry, and temperature stability. Sudden changes can be fatal. Pristine, stable water conditions are the primary care requirement. Regular small water changes (10–15% weekly) with matched water chemistry.