What tank size does a Black Ghost Knifefish need?

A Black Ghost Knifefish needs an aquarium of at least 600 litres (158.5 US gallons) with a footprint at least 180 cm (70.9 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Black Ghost Knifefish need?

Black Ghost Knifefish does best at 23–28 °C (73.4–82.4 °F), pH 6–8 and a general hardness of 5–19 °dGH.

Is the Black Ghost Knifefish suitable for beginners?

Black Ghost Knifefish is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.

Species library

Black Ghost Knifefish

Apteronotus albifrons

Apteronotidae

FishDifficulty: ●●●●●Data: well-established

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About

The black ghost knifefish is a nocturnal, electrolocating oddball from the Amazon and Paraguay-Paraná basins, sold at 8-10 cm and reaching 45-50 cm. It has no dorsal fin and swims by rippling one long anal fin, hovering, reversing and swimming vertically with equal ease, while a weak electric organ in its tail lets it navigate and hunt in complete darkness. It is scaleless, which makes it unusually sensitive to nitrate, dissolved organics and the copper- or formalin-based whitespot treatments most community tanks rely on. Adults are territorial towards each other and towards other electric fish, and they will eat any tankmate small enough to swallow at night.

Care

A 50 cm fish that needs roughly 600 L and 180 cm of swimming length as an adult — buy that tank on the day you buy the 8 cm juvenile, not later. One per tank, 25-27 °C, sand, dim light, caves and lengths of pipe to lie up in, strong filtration, GH of at least 5 for a scaleless fish, and nitrate under 20 ppm. Tankmates must be calm and too large to swallow — think 15 cm and up; dose medications at half strength.

Diet

Carnivorous night hunter taking insect larvae, worms, small crustaceans and small fish. Feed frozen and live foods plus sinking pellets after dark.

Tankmate compatibility

Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Telling males from females

There is no reliable way to sex this species by eye. That is the honest answer, not a gap in our data.

All the methods, with diagrams

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Sold in Lithuania

These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.

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Frequently asked questions

What tank size does a Black Ghost Knifefish need?: A Black Ghost Knifefish needs an aquarium of at least 600 litres (158.5 US gallons) with a footprint at least 180 cm (70.9 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Black Ghost Knifefish need?: Black Ghost Knifefish does best at 23–28 °C (73.4–82.4 °F), pH 6–8 and a general hardness of 5–19 °dGH.
Is the Black Ghost Knifefish suitable for beginners?: Black Ghost Knifefish is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.

Sources

Water & tank

Temperature23–28°C

Optimal temp.25–27°C

pH6–8

Hardness (GH)5–19°d

Carbonate (KH)1–10°d

Adult size50 cm

Min. volume≥ 600 L

Min. tank length≥ 180 cm

Swimming zoneAll levels

TemperamentSemi-aggressive

Water typeFreshwater

FlowModerate

Lifespan~12 yrs

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