Red-line Rasbora

The red-line rasbora was long known as Rasbora pauciperforata; today it is placed in the genus Trigonopoma. Its slender, elongated body is olive brown. Directly above the thin dark stripe that runs from behind the eye to the caudal peduncle is a copper-red line that glows as it catches the light. This line looks best against a dark substrate and in dim light.

It grows to about 6 cm, reaching at most 7 cm. It is a peaceful and somewhat retiring species; it shows its color and natural behavior when kept in a planted aquarium with calm, small companions rather than large, boisterous fish.

It lives in the forested lowlands of the Malay Peninsula and Sumatra, in swamps and slow-flowing blackwater streams. The water is dark from tannins, very soft and acidic; the bottom is covered with leaves and there is dense vegetation along the banks.

• Volume: at least 60 liters and 60 cm in length for a group of 8–10.
• Water: 24–27°C, pH 5.5–6.8, soft water. Slightly tannin-stained water with dried leaves and roots is recommended.
• Light: dim; floating plants diffuse the light and put the fish at ease.
• Layout: dense plants along the sides, open space in the middle.
• Lid: it may jump when startled; keep the aquarium covered.

Omnivorous, but in the wild it feeds mainly on small insects and their larvae. In the aquarium it accepts flakes and small granules; frozen cyclops, daphnia, brine shrimp and mosquito larvae noticeably enliven its colors.

Peaceful and calm; somewhat timid. It swims as a group in the middle and upper layers, close to the plants. In a large group and a calm setting it comes out into the open; among hectic tankmates it hides.

Good companions: other rasboras, small tetras, Boraras species, corydoras, kuhli loaches, otocinclus, dwarf gouramis, shrimp.

Avoid: large, active fish, aggressive cichlids, fin nippers.

At least 8, ideally 12 or more individuals. The size of the group directly affects the fish's confidence; kept in small numbers, their colors fade and they hide. The male-to-female ratio is not important.

It scatters its eggs among fine-leaved plants or moss; there is no parental care. Breeding requires a separate aquarium with very soft, acidic water, dim light and dense moss. Since the adults eat the eggs, they are removed after spawning. The fry are fed infusoria, then newly hatched brine shrimp. It is harder to breed in the aquarium than other rasboras.

• Hard water: color loss and susceptibility to disease occur after long periods in hard, alkaline water.
• Stress: in an open, brightly lit aquarium it stays skittish and does not feed properly.
• Water quality: a 25% weekly water change and stable values are sufficient.

Males are slimmer and their copper-red lines are brighter. Females have a fuller belly and slightly paler colors.