Can black ghost knives live with upside down catfish?

Verdict

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

Black ghost knife73–82°F · pH 6–8

Upside down catfish72–79°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 upside down catfish do.
Watch outBlack ghost knives grow to 15 inches and need 125 gallons, far more than a tank set up for upside down catfish.

What works

Both are fine at 73–79°F.
pH 6–7.5 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

	Black ghost knife	Upside down catfish
Temperature	73–82 °F	72–79 °F
pH	6–8	6–7.5
Adult size	15.0 in	4.0 in
Minimum tank	125 gal	30 gal
Temperament	Semi-aggressive	Peaceful
Swims at	Bottom	Bottom
Group	One per tank	Groups of 3+
Diet	Carnivore	Omnivore

Better tank mates for black ghost knives

All black ghost knife tank mates

Better tank mates for upside down catfish

All upside down catfish tank mates

Questions

Can black ghost knives live with upside down catfish?

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

What temperature suits both black ghost knives and upside down catfish?

73–79 °F. Black ghost knives need 73–82 °F, upside down catfish need 72–79 °F.

What size tank do black ghost knives and upside down catfish need together?

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