Glowlight Rasbora

Trigonostigma hengeli, commonly known as the Hengel’s Rasbora or Glowlight Rasbora, is a small schooling fish native to Southeast Asia, where it inhabits blackwater and peat swamp ecosystems across parts of southern Thailand, Peninsular Malaysia, and Borneo. Its known distribution includes forested lowland streams and shaded tributaries within the Pahang, Johor, and Muar river basins, along with localized populations in western and central Borneo. These waters are typically warm, soft, acidic, and heavily stained with tannins from decomposing leaf litter, creating calm, dimly lit environments beneath dense canopy cover.

Adult Trigonostigma hengeli grows to about 1.25 inches in length and is characterized by its delicate translucent body and the narrow, glowing orange wedge along the flank bordered by a thin black line. The species is similar to Trigonostigma heteromorpha and T. espei but is distinguishable by its slender profile and the more refined, luminous wedge pattern. When kept in proper schools, the coordinated movement and subtle coloration create a vibrant, shimmering midwater display.

A tank of at least 15 to 20 gallons is suitable for a school, with larger groups offering the most natural behavior. Aquariums designed with driftwood, floating plants, leaf litter, and gentle planting recreate their native conditions and provide security. Soft lighting, darker substrates, and moderate shading help bring out their warm coloration and reduce stress.

Water conditions for Trigonostigma hengeli should reflect the soft, acidic blackwaters of their natural habitat. Ideal parameters include temperatures between 74 and 82°F, a pH of 5.0 to 6.8, and low mineral content. They thrive in clean, well-oxygenated water with gentle flow. The addition of botanicals can help maintain tannin-rich water that mirrors the wild environment.

Feeding is simple and varied. In the wild they feed on tiny insects, microcrustaceans, and zooplankton drifting within the water column. In the aquarium they readily accept micro-pellets, crushed flake foods, baby brine shrimp, daphnia, and small frozen fare. A diverse diet enhances their coloration and keeps their activity level high.

Hengel’s Rasboras are peaceful, highly social fish that should be kept in schools of eight or more to ensure proper behavior and reduce skittishness. They coexist easily with other gentle Southeast Asian species such as small rasboras, peaceful gouramis, shrimp, and bottom dwellers that appreciate similar water conditions. Their calm nature makes them ideal residents of planted community setups.

Breeding Trigonostigma hengeli is possible in captivity. They are egg scatterers that often deposit adhesive eggs on the underside of broad leaves or similar surfaces. Soft, acidic water and dim lighting promote spawning. Adults may eat the eggs, so providing dense coverage or removing the parents improves fry survival.

Trigonostigma hengeli is a graceful and subtly radiant schooling fish that thrives in quiet, planted aquariums with soft, acidic, tea-colored water, offering elegant movement, gentle behavior, and a warm glowing presence in the midwater zone.