Black ruby barb guide

Common name: Black ruby barb
Scientific name: Pethia nigrofasciata
Category: Freshwater fish
Group: Barbs
Environment: Cool-to-warm mature freshwater aquarium with shaded stream structure and open swimming room
Origin: Wet-zone river basins of south-western Sri Lanka, from the Attanagalu and Kelani region southwards
Care level: Intermediate
Adult size: Approximately 6–7 cm total length
Expected lifespan: Plan for approximately 5–8 years and potentially longer under cool, oxygen-rich group care.
Minimum housing: At least 100 L with an 80 cm or longer footprint for ten or more fish
Temperature: 20–26 °C
pH: Unknown; match source stock and avoid abrupt change
Hardness / minerals: Unknown; stable soft to moderate mineral content is preferable to chemical chasing
Salinity: Freshwater, 0 ppt; routine salt addition is not recommended
Lighting: Moderate with shaded planted or wooded areas
Placement / zone: Middle and lower water
Filtration: Use mature biological filtration sized for the complete adult black ruby barb group, with guarded intakes and accessible mechanical capture. Keep flow moderate with strong surface exchange and open schooling water where the fish lives, and maintain undetectable ammonia and nitrite.
Aeration: Maintain reliable surface agitation and oxygen exchange at all times. Increase aeration during warm weather, medication, transport recovery, heavy feeding or any sign of rapid breathing.
Maintenance: Perform regular matched-water changes guided by nitrate and waste, remove uneaten food and trapped detritus, clean mechanical media without disrupting the biofilter, and record feeding, body condition, respiration and aggression.

Identity and search names

Single-species profile for the Sri Lankan endemic Pethia nigrofasciata. Puntius nigrofasciatus is an older combination still encountered in trade records.

Search names: Purplehead barb, Ruby barb, Puntius nigrofasciatus

Environment and housing

Provide a long aquarium with shaded plant or wood cover, open swimming space, good oxygenation and mature filtration.

Social structure: Keep at least ten with both sexes represented

Feeding and nutrition

Feeding ecology: Omnivore taking small invertebrates, detrital foods and plant material

Feeding routine: Offer one or two small varied meals daily

Breeding, reproduction or spread

Egg scatterer among fine plants or spawning media; adults provide no care

Detailed care and app-ready planning

Identity scope: Single-species profile for the Sri Lankan endemic Pethia nigrofasciata. Puntius nigrofasciatus is an older combination still encountered in trade records.
Adult size and space: Adults are roughly 6–7 cm total length. Use at least 100 L with 80 cm or more of frontage for a group of ten or more.
Social structure: Maintain at least ten with both sexes represented. Group living distributes chasing and allows normal male display without one fish absorbing all attention.
Swimming zone or placement: Middle and lower water, with frequent movement between open lanes and shaded margins.
Feeding ecology: Omnivorous stream fish consuming small invertebrates, detrital material and plant matter.
Feeding plan: Use quality small pellets or flakes, algae-rich foods and small frozen invertebrates once or twice daily. Prevent dominant males from monopolising food.
Water stability: Maintain 20–26 °C with high oxygen and zero ammonia or nitrite. A universal pH and hardness range was not independently established; match the source population and avoid abrupt change.
Habitat structure: Use shaded planted margins, wood, leaf litter used hygienically, open swimming room and steady circulation without forcing fish against the current.
Compatibility plan: Choose similarly active peaceful fish. Avoid long-finned slow swimmers and species requiring substantially warmer water.
Breeding or reproduction plan: Use a separate planted or mesh-bottom spawning aquarium, remove adults after egg deposition and rear fry on appropriately small first foods.
Quarantine: Quarantine in a separate cycled aquarium with dedicated nets, containers and siphons. Match temperature and mineral chemistry gradually, confirm normal feeding, respiration, skin, fins and waste, and never pour transport water into the established aquarium.
Welfare checks: Check colour, school cohesion, fin edges, body weight, respiration and whether subordinate fish feed.
Biosecurity and release: Never release fish, fry, eggs, aquarium water, sediment, plants or foods into drains, dams or natural waterways. Check the exact accepted scientific name in current BICON and applicable South Australian rules before import, sale or movement; import eligibility does not authorise release or wild collection.
Main risk: Small groups and warm poorly oxygenated water suppress normal behaviour and can concentrate fin-nipping.
Adult projected load: Project biological load from the full adult black ruby barb group, adult body mass, feeding pattern, activity and social requirement rather than juvenile sale size. A group of robust barbs creates a moderate-to-high feeding and oxygen load, especially when males display and chase.
Filtration: Use mature biological filtration sized for the complete adult black ruby barb group, with guarded intakes and accessible mechanical capture. Keep flow moderate with strong surface exchange and open schooling water where the fish lives, and maintain undetectable ammonia and nitrite.
Aeration: Maintain reliable surface agitation and oxygen exchange at all times. Increase aeration during warm weather, medication, transport recovery, heavy feeding or any sign of rapid breathing.
Maintenance: Perform regular matched-water changes guided by nitrate and waste, remove uneaten food and trapped detritus, clean mechanical media without disrupting the biofilter, and record feeding, body condition, respiration and aggression.
Overridable warnings: Non-overridable: do not accept persistent ammonia or nitrite, oxygen distress, starvation, chronic aggression or inadequate adult space. Different equipment, stocking or maintenance methods may be used only when measured water quality and adult welfare remain equivalent or better. A proper group, cooler oxygen-rich water and enough footprint to distribute chasing cannot be overridden by temporary calm behaviour.

Compatibility, welfare and risk

Compatibility: Use active peaceful tankmates of similar size; avoid delicate long-finned fish and very slow feeders.

Welfare: Monitor colour, school cohesion, fin condition, body weight and access to food; washed-out colour can indicate stress rather than sex alone.

Main warning: Wild populations are geographically structured and conservation-sensitive. Prefer documented captive-bred fish and never mix conservation lines without records.

Biosecurity and release

Never release fish, fry, eggs, aquarium water, sediment, plants or foods into drains, dams or natural waterways. Check the exact accepted scientific name in current BICON and applicable South Australian rules before import, sale or movement; import eligibility does not authorise release or wild collection.

Black ruby barb