Can cardinal tetras live with serpae tetras?

Verdict
Yes

Yes. Cardinal tetras and serpae tetras make a good pair. Both are fine at 76–79°F. Plan on at least 20 gal.

Cardinal tetraCardinal tetra76–84°F · pH 4.6–7 Serpae tetraSerpae tetra72–79°F · pH 6–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 76–79°Cardinal tetra 76–84°Serpae tetra 72–79°
The green band is the temperature range both can live in.
456789Both: 6–7Cardinal tetra 4.6–7Serpae tetra 6–7.5
The green band is the pH both tolerate.

Size to scale

Cardinal tetra · 2 inSerpae tetra · 1.75 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 tetraSerpae tetra
Temperature76–84 °F72–79 °F
pH4.6–76–7.5
Adult size2.0 in1.75 in
Minimum tank20 gal20 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 serpae tetras

All serpae tetra tank mates

Questions

Can cardinal tetras live with serpae tetras?

Yes. Cardinal tetras and serpae tetras make a good pair. Both are fine at 76–79°F. Plan on at least 20 gal.

What temperature suits both cardinal tetras and serpae tetras?

76–79 °F. Cardinal tetras need 76–84 °F, serpae tetras need 72–79 °F.

What size tank do cardinal tetras and serpae tetras need together?

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