Black Ruby Barb (Pethia nigrofasciata)

Pethia nigrofasciata, the Black Ruby Barb, is endemic to Sri Lanka, where it inhabits slow to moderately flowing streams and rivers in the hill and lowland zones, particularly in the Kelani and Kalu Ganga river systems. This species has the conservation status of Vulnerable due to habitat destruction and overcollection, though most aquarium specimens are captive-bred.

The Black Ruby Barb is arguably one of the most beautiful barb species in the hobby — particularly the males. Outside of breeding condition, males display a golden-olive to reddish body with three dark vertical bars. As breeding season approaches and during spawning condition, the front half of the male's body transforms into a deep, velvety black while the rear half intensifies to a brilliant ruby red — a spectacular and dramatic colour change.

Females are less dramatically coloured, displaying golden-brown to olive bodies with the three dark bars retained year-round. Despite the dimorphism, females are attractively marked and contribute to the school's visual appeal.

This species is peaceful and far less prone to fin-nipping than many barb species, making it more compatible with a wider range of tank mates including long-finned species. Schools of eight or more display the most natural behaviour and produce the best visual impact, especially when the males are in breeding colour.

Tank Setup: A minimum 80-litre tank for a school of eight. Provide moderate water flow, dense side and background planting (Cryptocoryne, Java fern, Vallisneria), open mid-water swimming lanes, and darker substrate that enhances the ruby-red colouration. Avoid very bright lighting — subdued light makes males colour up more intensely.

Water Parameters: Temperature 20–25°C; pH 6.0–7.5; GH 4–15 °dH; KH 2–8 °dH. Prefers slightly cooler water than many tropical fish, reflecting its highland Sri Lankan origin. Avoid sustained temperatures above 26°C.

Feeding: Omnivore. Accepts quality flake, micro pellets, frozen bloodworm, brine shrimp, Daphnia, and blanched vegetables (zucchini, spinach). Feed two to three times daily. Varied diet maintains male breeding colour.

Tank Mates: One of the more peaceful barb species. Compatible with most community fish: tetras, rasboras, gouramis, corydoras, and even long-finned fish (though monitoring is still recommended). Avoid very small nano fish that may be harassed.

Behaviour: Active, lively schooling fish. Groups of 8+ show tight schooling and fascinating male display behaviour. Less fin-nipping tendency than Tiger or Rosy Barbs. Males court females with impressive colour display.

Health: Hardy once established. Prefers cooler temperatures — prone to disease in overly warm water (above 26°C sustained). Weekly 25% water changes essential. Monitor for ich during temperature fluctuations.