Should I buy it?
Black ruby barb
Pethia nigrofasciata
Also known as: purplehead barb
Males develop deep red-and-black colouring during display, especially near spawning. A school of eight in a planted tank produces constant visual competition and colour.
Black ruby barb tank mates · 100L tank size hub
peaceful · intermediate care
Sources & confidencehigh · partially verified · beginner: caution
Checked against several solid care sources that mostly agree. Numbers here are a careful starting point. Your tap water, tank size, and habits decide the rest. How we evaluate.
Best for: Planted community tanks 100L or more with a school of six or more and peaceful mid-size companions.
Avoid if: You keep long-finned or nano fish. Black ruby barbs are mild fin-nippers in small groups.
Common mistakeKeeping three black ruby barbs in a community is how keepers invent focused chasing on each other and on long-finned neighbours. A short trio has nowhere to dilute pecking order. Stock six or more in at least 100L with softish planted cover — not a show trio for colour.
Top things that go wrong
- Group welfare — not a solo display fish. Plan at least **6** together for normal behaviour; smaller groups often mean stress, colour loss, or nipping depending on species.
- Shrimp & snails. Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
What most shops don't tell you
- 1.Myth: black ruby barbs are peaceful show barbs that stay calm as a trio in any community. Reality: small groups concentrate aggression — they need six or more in planted softish water, and long-finned tank mates pay for under-stocking first.
- 2.Housed in hard, alkaline, brightly lit bare tanks with no cover.
- 3.Kept as a single show fish without a same-species group of six or more.
- 4.Check temperature overlap with your other fish. These do best a few degrees cooler than classic Amazon tetra setups. Feed greens and small foods, easy on the protein.
About this species
Black ruby barbs are small cyprinids from cool, shaded forest streams in Sri Lanka. Mature males flush deep ruby in soft, planted, dim water held in a proper school. The wild population is of conservation concern, so buy farmed stock.
- Brown / hockey-stick pencilfish100L min · same group, comparable tank size
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- Gold / Chinese barb120L min · same group, comparable tank size
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- Odessa Barb120L min · same group, comparable tank size
- Pearl Danio80L min · same group, comparable tank size
- Cherry Barb60L min · same group, similar adult size
- Dwarf pencilfish60L min · same group, similar adult size
- Adolfoi coryalso intermediate peaceful, similar tank size
- African freshwater butterflyfishalso intermediate peaceful, similar tank size
- Bamboo Shrimpalso intermediate peaceful, similar tank size
- Boesemani Rainbowfishalso intermediate peaceful, similar tank size
- Bolivian Ramalso intermediate peaceful, similar tank size
- Brown / hockey-stick pencilfishalso intermediate peaceful, similar tank size
No reverse lookups listed yet.
Plan grid
Key limits are above. Here: pH band, swim level, bioload, and activity.
Swim zones
Care snapshot
Quick compare before you buy. Not a score of how “good” the fish is.
- Beginner ease32
- Peacefulness82
- Community fit74
- Small-tank fit100
- Hardiness44
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Example setups
Starting points only. Run the pair checker for every fish you add.
Rough 100L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safer directions include: Ember Tetra, Harlequin Rasbora, Neon Tetra.
Prioritise 6+ of Black ruby barb in 100L+ with filtration sized for messy feeding — add only mates that already pass pair checks with this species.
Avoid “one of everything” baskets — Black ruby barb belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Compatibility
Tank mates for Black ruby barb
Usually safer (engine GOOD): Ember Tetra, Harlequin Rasbora, Neon Tetra. Conditional (CAUTION — read the pair page before buying): Angelfish, Corydoras Catfish, Dwarf Gourami, German Blue Ram, Tiger Barb. Avoid (RISKY): African Cichlid, Green Terror, Jack Dempsey, Oscar. Every name links to a live pair check — the lists are a shortlist, not a stocking plan.
Usually safer
Open a pair page with this fish as the starting point.
Needs planning
Read the blocking rule on each pair page before experimenting.
Usually avoid
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Black ruby barb + Ember Tetra
- Try Ember Tetra — open the pair check.
- Try Harlequin Rasbora — open the pair check.
- Try Neon Tetra — open the pair check.
Behaviour and temperament
Black ruby barbs are generally peaceful schoolers that stay calmer in honest numbers of six or more. Under-grouped fish redirect nipping onto fins and each other. Stress shows as chasing lanes and torn neighbours when the school is too small or the tank is bare and bright.
What sets them off
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper; stressed or crowded individuals can still test fins.
Predation: Not a predator toward similarly sized community fish; fry and dwarf shrimp are still fair game for most species.
Territory: Holds a patch (cave, corner, or surface). Break sight lines so neighbours can pass.
Planted tanks: excellent — easy plant ideas
In the glass: typical and warning signs
- Six or more hold midwater among plants with males flashing ruby flanks.
- In-school sparkle and mild line order are normal ownership, not a reason to break the group.
- Persistent chasing in a trio means the group size failed before mystery disease.
- Faded colour in hard bare tanks usually means cover and chemistry first.
- Short groups concentrate nips on long-finned neighbours.
- They rarely start wars when stocked as a real school with calm dither.
- Increase school size before blaming a single ‘mean’ fish.
- Remove long-finned targets if a short group will not be expanded.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Water, food, and grouping
Hardness
soft
Diet
omnivore
Black ruby barbs are midwater omnivores that take quality flake, micro-pellets, and frozen foods once a school of six or more is settled. Food that only hits the sand leaves the group thin while bottom fish look fine. Offer a staple plus daphnia or bloodworm a few times a week, and feed where the school holds so shy individuals still reach meals among plants.
Shrimp & snails
Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
Schooling species — buy 6+ together. Smaller groups stress and lose colour.
- Hold 22 to 26 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 6 to 6.5 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Schooling species. Buy 6 or more from the same tank on the same day before adding any centrepiece fish.
- Tank volume meets or exceeds 100L published minimum for adults.
- You can stock at least 6 individuals (group welfare).
- Heater can hold 22–26°C without cooking cooler-water tank mates.
- No known fin-nippers paired with long-finned fish unless you accept documented risk.
Explore and stocking hubs
Tank-mates hub, matching guides, category peers, and litre stocking lists around this species’ minimum tank.
Plan with tools
Check mates as pairs first, then add this fish in the tank builder for the full stocking.
Filtration & heating
A 100L minimum tank needs a filter rated for at least 400L/hr turnover and a heater to hold 22–26°C reliably.
Plant suggestions
Black ruby barb does well in planted tanks. Plants compatible with 22–26°C and pH 6–6.5:
Research: partially verified · Confidence: high · 4 linked source(s). We do not invent citations.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Pethia nigrofasciata
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Pethia nigrofasciata
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Pethia nigrofasciata
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
- Wikipedia. Black ruby barb
Overview and range. Cross-check all aquarium numbers against specialist care sheets before buying.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
Common questions about Black ruby barb
- How big do Black ruby barb get?
- Black ruby barb adults reach about 6 cm. Shop fish look smaller; stock for the adult length.
- What size tank does Black ruby barb need?
- 100L is the planning floor for adult swimming space and bioload. A 122L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.
- Are Black ruby barb aggressive?
- Black ruby barbs are generally peaceful schoolers that stay calmer in honest numbers of six or more. Under-grouped fish redirect nipping onto fins and each other. Stress shows as chasing lanes and torn neighbours when the school is too small or the tank is bare and bright.
- Do Black ruby barb need to be kept in a group?
- Schooling species — buy 6+ together. Smaller groups stress and lose colour.
- What is the most common mistake with Black ruby barb?
- Keeping three black ruby barbs in a community is how keepers invent focused chasing on each other and on long-finned neighbours. A short trio has nowhere to dilute pecking order. Stock six or more in at least 100L with softish planted cover — not a show trio for colour.
- What fish can live with Black ruby barb?
- The Black ruby barb profile lists Ember Tetra, Harlequin Rasbora, Neon Tetra among its safer pairings (engine-checked GOOD). Angelfish, Corydoras Catfish, Dwarf Gourami, German Blue Ram are conditional (CAUTION): workable only with the specific conditions on each pair page. Avoid African Cichlid, Green Terror, Jack Dempsey, Oscar (RISKY). Run the pair checker for your exact water and tank size before stocking.