Can black ghost knives live with rosy barbs?

Verdict

No. Black ghost knives and rosy barbs should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 4 inches rosy barbs do.

Black ghost knife73–82°F · pH 6–8

Rosy barb64–77°F · pH 6–7.5

What to watch

Deal breakerAn adult black ghost knife eats fish that fit in its mouth, and at 4 inches rosy barbs do.
Watch outBlack ghost knives grow to 15 inches and need 125 gallons, far more than a tank set up for rosy barbs.

What works

Both are fine at 73–77°F.
pH 6–7.5 suits both.
They use different parts of the tank: black ghost knives the bottom, rosy barbs the mid.

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

	Black ghost knife	Rosy barb
Temperature	73–82 °F	64–77 °F
pH	6–8	6–7.5
Adult size	15.0 in	4.0 in
Minimum tank	125 gal	30 gal
Temperament	Semi-aggressive	Semi-aggressive
Swims at	Bottom	Middle
Group	One per tank	Groups of 6+
Diet	Carnivore	Omnivore

Better tank mates for black ghost knives

All black ghost knife tank mates

Better tank mates for rosy barbs

All rosy barb tank mates

Questions

Can black ghost knives live with rosy barbs?

No. Black ghost knives and rosy barbs should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 4 inches rosy barbs do.

What temperature suits both black ghost knives and rosy barbs?

73–77 °F. Black ghost knives need 73–82 °F, rosy barbs need 64–77 °F.

What size tank do black ghost knives and rosy barbs need together?

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