Can cardinal tetras live with black skirt tetras?

Verdict
Yes

Yes. Cardinal tetras and black skirt tetras get along in the same tank. Both are fine at 76–80°F. Plan on at least 20 gal.

Cardinal tetraCardinal tetra76–84°F · pH 4.6–7 Black skirt tetraBlack skirt tetra70–80°F · pH 6–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 76–80°Cardinal tetra 76–84°Black skirt tetra 70–80°
The green band is the temperature range both can live in.
456789Both: 6–7Cardinal tetra 4.6–7Black skirt tetra 6–7.5
The green band is the pH both tolerate.

Size to scale

Cardinal tetra · 2 inBlack skirt tetra · 2.5 in0"1"2"3"4"5"6"
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

Cardinal tetraBlack skirt tetra
Temperature76–84 °F70–80 °F
pH4.6–76–7.5
Adult size2.0 in2.5 in
Minimum tank20 gal15 gal
TemperamentPeacefulSemi-aggressive
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for cardinal tetras

All cardinal tetra tank mates

Better tank mates for black skirt tetras

All black skirt tetra tank mates

Questions

Can cardinal tetras live with black skirt tetras?

Yes. Cardinal tetras and black skirt tetras get along in the same tank. Both are fine at 76–80°F. Plan on at least 20 gal.

What temperature suits both cardinal tetras and black skirt tetras?

76–80 °F. Cardinal tetras need 76–84 °F, black skirt tetras need 70–80 °F.

What size tank do cardinal tetras and black skirt tetras need together?

At least 20 gal, set by the cardinal tetra. Add space for each extra fish.