Should I buy it?
Black ghost knifefish
Apteronotus albifrons
Also known as: black ghost, bgk, Black ghost, BGK
Fishori provides conservative planning guidance, not guarantees.
Based on typical aquarium care sources; details may vary between setups. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
A nocturnal predator at 45 cm that uses weak electric fields to navigate. Needs a large tank with caves and is highly sensitive to fin-nipping neighbours.
Best for
Specialist dedicated tanks 500L or more with low lighting, sand, and carefully selected large peaceful companions.
Avoid if
Standard community setups, tanks under 300L, or any fish that might compete for caves or nip fins.
Top things that go wrong
- Grows large or needs a very big footprint. Black ghost knifefish is often sold at sizes that hide adult length (~45cm on file) and a published minimum near **500L**. Shop tanks are not adult housing.
- Fin-nipping risk in typical community layouts. Fin-nipping risk toward long-finned or slow tank mates when the school is understocked, bored, or kept in a tank too short to spread out in.
- Mouth gap vs tiny tank mates. Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
More issue cards below, after species context.
Common mistakeA black ghost with barbs or tetras. The knifefish fin is large and prominent; fin-nippers will damage it within days and stress the fish chronically.
Additional planning warnings
Specialist husbandry
Kept singly or as a paired setup. Check the species profile before doubling up in one tank.
Shrimp & snails
Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
What most shops don't tell you
- 1.Predation risk scales with gape, night feeding, and crowding. 'they grew up together' is a schedule, not a law.
- 2.Sold as a 12 cm 'ghost' for a 40 L showpiece, then growing past 40 cm in the same flat with no plan for an upgrade.
- 3.Lit bright all day. The fish stays hidden, eats poorly, and gets labelled shy when it is just wrong-lit.
- 4.Buy a tank for the adult, not the 12 cm shop juvenile. Provide a long pipe to hide in by day, dim ambient light, and no bite-sized dither in the same volume.
- 5.Advanced species — research stable parameters before buying.
About this species
Black ghost knifefish are weakly electric South American predators that hunt by electrolocation in the dark. Adults reach 40 to 50 cm, closer to a stingray-class fish than a community oddball. They need a 500 L or larger tank with caves, dim lighting, and no fish small enough to swallow.
- Senegal bichir300L min · same fish family
- Ropefish / reed fish200L min · same fish family
- African freshwater butterflyfish150L min · same fish family
- Golden Wonder Killifish80L min · same fish family
- American Flagfish60L min · same fish family
- Marbled Hatchetfish60L min · same fish family
- Pea Puffer40L min · same fish family
- Clown Killifish20L min · same fish family
No close matches on file.
No reverse lookups on file yet.
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease6
- Peacefulness0
- Community fit0
- Small-tank fit30
- Hardiness36
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Avoid “one of everything” baskets — Black ghost knifefish belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Tank mate intelligence
Use the "Often compatible" lists as a shortlist, not a stocking plan. Always run the pair tool and check the footprint of your actual tank first. Verify behaviour for Black ghost knifefish against your own reading before you buy.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Black ghost knifefish + Boesemani Rainbowfish
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Black ghost knifefish is semi-aggressive: stable in a calm tank, pushy with weaker fish when stressed or crowded. Fin-nipper when the school is understocked, bored, or kept in a tank too short to spread out in. Treats any fish small enough to fit in its mouth as food. Mouth size at adult length matters, not the prey's listed adult size. Holds territory on substrate, in caves, or at the surface film. Break the sight lines with hardscape to keep the resident off the visitor.
Stress / aggression triggers on file
- Small groups or boredom
- Long-finned or slow tank mates
- Bare tanks without structure
Fin nipping: Fin-nipping risk toward long-finned or slow tank mates when the school is understocked, bored, or kept in a tank too short to spread out in.
Predation: Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
Territory: Holds territory on substrate, in caves, or at the surface film. Break the line of sight with hardscape, and avoid placing the tank where the fish can see its own reflection.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Moderate pacing — not hyperactive, not motionless.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Chasing one individual repeatedly, torn fins on tank mates, or food theft every feed.
- Corner guarding, flaring, or body-blocking — territory is normal until it becomes relentless.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
soft
Diet
carnivore
Small invertebrates, frozen bloodworm or daphnia, and protein-rich prepared foods. Rotate the menu and feed by appetite rather than by clock.
Shrimp & snails
Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
Kept singly or as a paired setup. Check the species profile before doubling up in one tank.
Breeding behaviour depends on the species. Research before you buy a mixed-sex group of this fish.
- Hold 24 to 28 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 6 to 7.2 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Footprint: short wide tanks and tall narrow tanks fish differently for the same volume. Match the tank shape to the swim pattern, not just the litre count.
- Tank volume meets or exceeds 500L published minimum for adults.
- Heater can hold 24–28°C without cooking cooler-water tank mates.
- No known fin-nippers paired with long-finned fish unless you accept documented risk.
- No tank mates small enough to fit the adult mouth gap for this species.
- Filter maturity / stable parameters before adding sensitive stock.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 500L minimum tank needs a filter rated for at least 2000L/hr turnover and a heater to hold 24–28°C reliably.
Plant suggestions
Black ghost knifefish does well in planted tanks. Plants compatible with 24–28°C and pH 6–7.2:
Profile status: partially verified · Evidence tier: medium · 2 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- LiveAquaria. Black ghost knifefish (Apteronotus albifrons care sheet)
Primary: large-aquarium retailer care profile: very large tank, dim lighting, hiding, carnivore diet, and size expectations. Cross-check the stated minimum with your own footprint and filtration; Fishori uses a stricter home-aquarium minimum than a catalog line.
- FishBase. Apteronotus albifrons
Secondary: natural history and max length; weakly electric foraging in the dark. Translate into tank length and nocturnal feeding, not a neon-tetra list.
Evidence notes
- A Seriously Fish apteronotus-albifrons profile URL was not found (search returned the site 404). LiveAquaria is the best stable, aquarium-specific primary available without resorting to wiki mirrors; FishBase is kept for size and range context. Expect debate between hobby sources on true adult length and 'minimum tank' gallons.
- 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.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.