Can clown loaches live with black ghost knives?

Verdict
Yes

Yes. Clown loaches and black ghost knives get along in the same tank. Both are fine at 77–82°F. Plan on at least 125 gal.

Clown loachClown loach77–86°F · pH 6–7.5 Black ghost knifeBlack ghost knife73–82°F · pH 6–8

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 77–82°Clown loach 77–86°Black ghost knife 73–82°
The green band is the temperature range both can live in.
456789Both: 6–7.5Clown loach 6–7.5Black ghost knife 6–8
The green band is the pH both tolerate.

Size to scale

Clown loach · 8 inBlack ghost knife · 15 in0"2"4"6"8"10"12"14"
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

Clown loachBlack ghost knife
Temperature77–86 °F73–82 °F
pH6–7.56–8
Adult size8.0 in15.0 in
Minimum tank75 gal125 gal
TemperamentPeacefulSemi-aggressive
Swims atBottomBottom
GroupGroups of 5+One per tank
DietOmnivoreCarnivore

Better tank mates for clown loaches

All clown loach tank mates

Better tank mates for black ghost knives

All black ghost knife tank mates

Questions

Can clown loaches live with black ghost knives?

Yes. Clown loaches and black ghost knives get along in the same tank. Both are fine at 77–82°F. Plan on at least 125 gal.

What temperature suits both clown loaches and black ghost knives?

77–82 °F. Clown loaches need 77–86 °F, black ghost knives need 73–82 °F.

What size tank do clown loaches and black ghost knives need together?

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