Trigonostigma truncata is a small cyprinid from the slow-flowing, tannin-stained forest streams and peat swamps of Southeast Asia. A recently described species, it remains uncommon in the aquarium trade and is most easily distinguished from its close relatives by the more abruptly “cut-off” shape of its dark posterior body marking. Adults grow to around 1.5 inches (3.5–4 cm) in length, with a laterally compressed body that ranges in color from warm gold to coppery orange. The signature black wedge-mark begins just below the dorsal fin and tapers toward the belly in front of the caudal peduncle, but ends with a blunt rear edge rather than a long taper. Fins are translucent with a slight amber tint, and well-conditioned fish show richer body color, with males often slightly deeper in hue than females. A peaceful shoaler, T. truncata should be kept in groups of at least six, with larger numbers encouraging tighter grouping and more natural displays. In the aquarium, a sandy substrate, dense planting, and open swimming areas will replicate their native habitat. Floating vegetation, dim lighting, and leaf litter help reproduce blackwater conditions and enhance their colors. Ideal water conditions include a temperature of 73–82 °F (23–28 °C), a pH of 5.0–7.0, and soft to moderately soft water. Gentle filtration and very clean, stable conditions suit them best. Feeding is simple, as they accept quality micro-pellets or flakes and should be offered small live or frozen foods such as daphnia, cyclops, and baby brine shrimp to maintain condition and encourage breeding. They are egg-scattering spawners, depositing eggs among fine-leaved plants or spawning mops, and will consume them if given the chance. Fry are tiny and require the smallest live foods to start.
