Can red tail sharks live with black ghost knives?

Verdict

No. Red tail sharks and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 5 inches red tail sharks do.

Red tail shark72–79°F · pH 6.5–7.5

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 5 inches red tail sharks do.
Watch outRed tail sharks chase other bottom fish out of their patch.

What works

Both are fine at 73–79°F.
pH 6.5–7.5 suits both.

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

	Red tail shark	Black ghost knife
Temperature	72–79 °F	73–82 °F
pH	6.5–7.5	6–8
Adult size	5.0 in	15.0 in
Minimum tank	55 gal	125 gal
Temperament	Semi-aggressive	Semi-aggressive
Swims at	Bottom	Bottom
Group	One per tank	One per tank
Diet	Omnivore	Carnivore

Better tank mates for red tail sharks

All red tail shark tank mates

Better tank mates for black ghost knives

All black ghost knife tank mates

Questions

Can red tail sharks live with black ghost knives?

No. Red tail sharks and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 5 inches red tail sharks do.

What temperature suits both red tail sharks and black ghost knives?

73–79 °F. Red tail sharks need 72–79 °F, black ghost knives need 73–82 °F.

What size tank do red tail sharks and black ghost knives need together?

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