Can firemouth cichlids live with black ghost knives?

Verdict

No. Firemouth cichlids and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 6 inches firemouth cichlids do.

Firemouth cichlid75–86°F · pH 6.5–8

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 6 inches firemouth cichlids do.
Watch outBlack ghost knives grow to 15 inches and need 125 gallons, far more than a tank set up for firemouth cichlids.

What works

Both are fine at 75–82°F.
pH 6.5–8 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

	Firemouth cichlid	Black ghost knife
Temperature	75–86 °F	73–82 °F
pH	6.5–8	6–8
Adult size	6.0 in	15.0 in
Minimum tank	30 gal	125 gal
Temperament	Semi-aggressive	Semi-aggressive
Swims at	Bottom	Bottom
Group	Alone or in pairs	One per tank
Diet	Omnivore	Carnivore

Better tank mates for firemouth cichlids

All firemouth cichlid tank mates

Better tank mates for black ghost knives

All black ghost knife tank mates

Questions

Can firemouth cichlids live with black ghost knives?

No. Firemouth cichlids and black ghost knives should not share a tank. An adult black ghost knife eats fish that fit in its mouth, and at 6 inches firemouth cichlids do.

What temperature suits both firemouth cichlids and black ghost knives?

75–82 °F. Firemouth cichlids need 75–86 °F, black ghost knives need 73–82 °F.

What size tank do firemouth cichlids and black ghost knives need together?

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