Black Ghost Knifefish: Tank Size, Tank Mates and How Many to Keep

The black ghost knifefish ripples through the water like a ribbon and finds its way with weak electric signals. It grows very large and needs a very big tank.

Adult size
15.7 in40 cm
Smallest tank
151 gallons570 liters
How many
One only
Temperature
73–82 °F23–28 °C
pH
6–7.5
Temperament
Semi-aggressive
Swims
On the bottom
Heater needed
Yes

What size tank does a black ghost knifefish need?

At least 150 gallons (570 liters). The smallest standard tank that works is the 150 gallon. A bigger tank is always easier to keep stable. We give the size for an adult fish, because the small fish in the shop will grow. Scientific name: Apteronotus albifrons.

How many black ghost knifefish in each tank size?

This is how many each standard tank carries comfortably if black ghost knifefish are the only fish in it. Share the tank with other species and the number goes down.

None. No common tank size up to 125 gallons is big enough for an adult black ghost knifefish.

Check black ghost knifefish against your own tank and other fish

Good to know

  • Grows to 40 cm or more and is active at night.
  • Keep one per tank. Two will fight over the floor.
  • It eats fish small enough to swallow. Choose tankmates at least half its length.

Tank mates for black ghost knifefish

These animals like the same water, are a safe size, and have a temper that fits. It is a match on paper: always watch new tankmates for the first week.

Poor matches

  • Betta: Black ghost knifefish (about 16 in) can eat betta (about 2.6 in).
  • Fancy goldfish: Goldfish do best with other fancy goldfish.

Questions and answers

What size tank does a black ghost knifefish need?

At least 150 gallons (570 liters). The smallest standard tank that works is the 150 gallon. A bigger tank is always easier to keep stable.

How many black ghost knifefish should be kept together?

Just one. Black ghost knifefish adults fight each other in a home tank.

Can black ghost knifefish live in a 10 gallon tank?

No. Black ghost knifefish needs at least 150 gallons (570 liters), and grows to 16 in (40 cm), far too long for a 20 inch tank.

What temperature do black ghost knifefish need?

73–82 °F (23–28 °C), with a pH of 6–7.5. In most homes that means a heater.

Can black ghost knifefish live with a betta?

It is not a good match. Black ghost knifefish (about 16 in) can eat betta (about 2.6 in).

More fish

Adult size, tank size and water ranges follow the mainstream care consensus (Seriously Fish species profiles and FishBase maximum lengths). Where sources differ we use the more cautious figure. Stocking numbers come from our stocking calculator.