Can congo tetras live with black ghost knives?

Verdict

No. Congo tetras and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 3 inches congo tetras do.

Congo tetra73–82°F · pH 6–7.5

Black ghost knife73–82°F · pH 6–8

What to watch

Deal breakerAn adult black ghost knife eats fish that fit in its mouth, and at 3 inches congo tetras do.
Watch outBlack ghost knives grow to 15 inches and need 125 gallons, far more than a tank set up for congo tetras.

What works

Both are fine at 73–82°F.
pH 6–7.5 suits both.
They use different parts of the tank: congo tetras the mid, black ghost knives the bottom.

Water side by side

The green band is the temperature range both can live in.

The green band is the pH both tolerate.

Size to scale

Adult length in an aquarium. A fish can swallow anything that fits in its mouth, roughly a third to half its own length for predators.

Care at a glance

	Congo tetra	Black ghost knife
Temperature	73–82 °F	73–82 °F
pH	6–7.5	6–8
Adult size	3.0 in	15.0 in
Minimum tank	30 gal	125 gal
Temperament	Peaceful	Semi-aggressive
Swims at	Middle	Bottom
Group	Groups of 6+	One per tank
Diet	Omnivore	Carnivore

Better tank mates for congo tetras

All congo tetra tank mates

Better tank mates for black ghost knives

All black ghost knife tank mates

Questions

Can congo tetras live with black ghost knives?

No. Congo tetras and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 3 inches congo tetras do.

What temperature suits both congo tetras and black ghost knives?

73–82 °F. Congo tetras need 73–82 °F, black ghost knives need 73–82 °F.

What size tank do congo tetras and black ghost knives need together?

At least 125 gal, set by the black ghost knife. Add space for each extra fish.