Black ghost knifefish care guide

Plan a tank with black ghost knifefishSee all tank mates

Black ghost knifefish quick facts

• Known jumper: keep a tight-fitting lid.
• Needs sand or smooth, fine gravel to protect its barbels and belly.

Tank setup

An adult needs at least 125 gallons (473 L) in a tank about 6 ft (180 cm) long and 2 ft (60 cm) front to back. Juveniles grow fast and outgrow a 55-gallon tank in about a year. Give it a tube or cave just big enough to hide in, soft sand, dim light and a tight lid.

How many black ghost knifefish in a tank?

The smallest common tank that suits black ghost knifefish is a 125 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

Numbers are bioload limits only. Keep only one per tank.

Water parameters

Keep it at 24–28 °C (75–82 °F), pH 6.5–7.8 and 5–12 dGH. Poor or unstable water quickly leads to skin problems, so only add it to a mature, well-filtered tank. Change water every week to keep nitrate low.

Best tank mates for black ghost knifefish

These popular species share black ghost knifefish' water needs and temperament. See the full list of 29 good matches.

• Nerite snail

  2.5 cm (1 in) · 22–27°C (72–81°F)

• Angelfish

  15 cm (5.9 in) · 24–29°C (75–84°F)

• Oscar

  30 cm (11.8 in) · 23–27°C (73–81°F)

• Assassin snail

  2.5 cm (1 in) · 22–27°C (72–81°F)

• Ramshorn snail

  2 cm (0.8 in) · 21–27°C (70–81°F)

• Malaysian trumpet snail

  2.5 cm (1 in) · 20–27°C (68–81°F)

• Mystery snail

  5 cm (2 in) · 21–26°C (70–79°F)

• Boesemani rainbowfish

  10 cm (3.9 in) · 26–29°C (79–84°F)

Avoid keeping black ghost knifefish with

• Betta fish: Black ghost knifefish can eat bettas: they're small enough to fit in its mouth once it's grown.
• Bronze corydoras: Black ghost knifefish can eat bronze corydoras: they're small enough to fit in its mouth once it's grown.
• Cherry shrimp: Black ghost knifefish eats small shrimp like cherry shrimp.
• Common goldfish: They need different temperatures: Black ghost knifefish 24–28°C (75–82°F), common goldfish 15–22°C (59–72°F).
• Fancy goldfish: They need different temperatures: Black ghost knifefish 24–28°C (75–82°F), fancy goldfish 18–23°C (64–73°F).
• Guppy: Black ghost knifefish can eat guppies: they're small enough to fit in its mouth once it's grown.

Feeding

A meat-eater that feeds mostly at night. Offer frozen or live bloodworms, brine shrimp, chopped earthworms and prawn, plus sinking carnivore pellets once it learns to take them. Feed after the lights go out so faster fish don't take everything first.

Behavior

Shy by day and active at night, it finds its way and its food with a weak electric field. It ignores fish too big to swallow but eats small tetras, guppies and shrimp. Two in one tank usually fight over hiding spots, so keep one. Pick calm tankmates of 4 in (10 cm) or more, such as angelfish, eartheater cichlids, silver dollars and peaceful catfish.

Breeding

Very rarely bred in home aquariums. In research tanks, spawning has been triggered by slowly lowering the water's conductivity to copy the rainy season. Most fish in shops are raised in large outdoor ponds, mainly in Indonesia. Males and females look almost the same.

Tips from experienced keepers

• Only buy a juvenile if you can give it a 6 ft (180 cm) tank within a year or two.
• Give it a clear tube or a length of PVC pipe to hide in. It will use it every day.
• Feed after the lights go out, when it is naturally active and hunting.
• Keep the lights dim or add floating plants. It comes out more often when the tank isn't brightly lit.
• Keep fish under about 3 in (8 cm), and all shrimp, out of its tank.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.

• seriouslyfish.com
• fishbase.se
• aquariumcoop.com
• aquariumsource.com
• en.wikipedia.org