Can red tail sharks live with black neon tetras?

Verdict
Yes

Yes. Red tail sharks and black neon tetras get along in the same tank. Both are fine at 73–79°F. Plan on at least 55 gal.

Red tail sharkRed tail shark72–79°F · pH 6.5–7.5 Black neon tetraBlack neon tetra73–81°F · pH 5.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 73–79°Red tail shark 72–79°Black neon tetra 73–81°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Red tail shark 6.5–7.5Black neon tetra 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Red tail shark · 5 inBlack neon tetra · 1.5 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

Red tail sharkBlack neon tetra
Temperature72–79 °F73–81 °F
pH6.5–7.55.5–7.5
Adult size5.0 in1.5 in
Minimum tank55 gal15 gal
TemperamentSemi-aggressivePeaceful
Swims atBottomMiddle
GroupOne per tankGroups of 6+
DietOmnivoreOmnivore

Better tank mates for red tail sharks

All red tail shark tank mates

Better tank mates for black neon tetras

All black neon tetra tank mates

Questions

Can red tail sharks live with black neon tetras?

Yes. Red tail sharks and black neon tetras get along in the same tank. Both are fine at 73–79°F. Plan on at least 55 gal.

What temperature suits both red tail sharks and black neon tetras?

73–79 °F. Red tail sharks need 72–79 °F, black neon tetras need 73–81 °F.

What size tank do red tail sharks and black neon tetras need together?

At least 55 gal, set by the red tail shark. Add space for each extra fish.