Chili Rasbora

The Chili Rasbora is a diminutive member of the Boraras genus, a group of miniature cyprinids often called micro-rasboras despite not being true rasboras. It is endemic to the blackwater peat swamps of southwestern Borneo, particularly in Kalimantan, Indonesia. First described scientifically in the late 1970s, it became a favorite in the aquarium trade for its intense red coloration and diminutive size, making it well suited to nano and planted tanks. Wild populations face pressure from habitat degradation linked to peat swamp deforestation and drainage for agriculture, and while still collected for the trade, sustainable captive breeding has reduced reliance on wild harvest.

The Chili Rasbora is one of the smallest freshwater aquarium fish, rarely exceeding 2.5 cm.

• Body: Deep red to orange-red, most intense in mature males
• Stripe: Thin dark horizontal line from eye to caudal base
• Fins: Translucent to reddish, unpaired fins often edged darker
• Size: Extremely small, roughly the size of a grain of rice to a small insect

Females are paler, rounder-bodied, and less vividly colored than males. It differs from similarly sized relatives like the Dwarf Rasbora by its more saturated red hue and finer body stripe.

Chili Rasboras live exclusively in the tea-colored, tannin-stained peat swamp waters of southwestern Borneo, where decomposing leaf litter creates highly acidic, soft, mineral-poor conditions. These blackwater habitats are typically shallow, slow-moving, and densely vegetated with overhanging plants and submerged root systems that provide cover from predators. Water temperatures remain warm and stable year-round, consistent with the equatorial climate. The dim, filtered light and low pH of these swamps are thought to contribute to the species' striking red pigmentation, which may aid camouflage against the reddish-brown tannic water. Habitat loss from peat swamp drainage and palm oil development threatens the fish's native range.

Chili Rasboras are peaceful, highly social micro-fish that form tight shoals when kept in groups, spending most of their time in the middle and lower water column. They feed on small invertebrates, zooplankton, and organic particles suspended in the water. Males display heightened red coloration and engage in brief fin-flaring displays to attract females, especially in the presence of fine-leaved plants or moss used as egg-scattering sites. They lay adhesive eggs with no parental care, and juveniles seek refuge among dense vegetation. Their small size makes them vulnerable to larger tankmates, so they rely heavily on shoaling and plant cover for protection.