Black ruby barb (Pethia nigrofasciata) care guide

Group
Freshwater fish
Other names
Ruby barb, Purple-headed barb, Purplehead barb
Family
Cyprinidae (Smiliogastrinae)
Origin
Endemic to south-western Sri Lanka, from the Kelani to the Nilwala basins; shaded, clear, shallow rainforest streams with sand and leaf litter, up to about 300 m altitude.
Water
freshwater
Maximum size
5.5 cm
Temperature
20–27°C
pH
5.5–7.5
Hardness
Soft to medium, 2–15 dGH
Minimum tank
72 litres
Care level
beginner
Temperament
peaceful

Care

The black ruby barb is a peaceful, colourful shoaling fish for a planted community tank. Keep a group of at least six to ten; single fish hide and stay pale, while in a group the males compete with each other and colour up strongly. A tank with a base of at least 80 × 30 cm (around 72 litres) is a sensible minimum. It shows its best colours in a heavily planted tank with a dark substrate, some floating plants, driftwood and a few dried leaves, which together mimic its shaded forest streams. Gentle to moderate water movement is welcome but the filtration need not be strong. Keep the water at about 20–27 °C and soft to medium. Farm-bred fish adapt to a pH of roughly 5.5–7.5, but wild fish prefer slightly acidic to neutral water. Both sexes are golden-yellow with broad dark vertical bars. Males are smaller, slimmer and more colourful; when in breeding condition the whole body darkens and the head and front of the body turn a rich reddish-purple, which gives the fish its name. Females are larger and plainer. The IUCN lists the species as Vulnerable. Its rainforest habitat is badly fragmented, and there are reports that the most brightly coloured wild fish are becoming scarcer. Sri Lanka restricts its export, so most fish in the trade are bred on farms; choose captive-bred stock. Sources: Seriously Fish (seriouslyfish.com/species/pethia-nigrofasciata/); FishBase (fishbase.se/summary/Pethia-nigrofasciata.html); Wikipedia (en.wikipedia.org/wiki/Blackrubybarb). Checked October 2026.

Diet

An omnivore that grazes on algae and detritus in the wild as well as taking small invertebrates. Offer a good flake or small granule that contains plant matter, with regular small live or frozen foods such as bloodworm, Daphnia and brine shrimp to bring out the best colour.

Breeding

An egg-scatterer that gives no parental care and will eat its eggs. Condition the adults well, then set up a separate dimly lit tank with mature, slightly acidic to neutral water at the top of its temperature range. Cover the base with mesh that lets the eggs fall through, or use glass marbles or fine-leaved plants such as Java moss. When the females look full of eggs, add one or two pairs, or a group of about six of each sex; spawning usually takes place the next morning. A female can lay over 100 eggs. Remove the adults once eggs are seen. The eggs hatch in 24–48 hours and the fry swim freely about a day later. Feed infusoria-sized foods for the first few days, then microworm and newly hatched brine shrimp.

Compatibility and tank mates

Generally very peaceful and a good community fish. Suitable tankmates include tetras, livebearers, rainbowfish, gouramis and other anabantoids, small catfish such as Corydoras, loaches and other small peaceful barbs, danios and rasboras. Avoid large or predatory fish, and keep it in a proper group so that males sort out their rivalry among themselves.

Last updated 5 October 2026. Community-edited care guide on Aquatic-Auctions.

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