Can harlequin rasboras live with black neon tetras?

Verdict
Yes

Yes. Harlequin rasboras and black neon tetras get along in the same tank. Both are fine at 73–80°F. Plan on at least 15 gal.

Harlequin rasboraHarlequin rasbora72–80°F · pH 6–7.5 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: 73–80°Harlequin rasbora 72–80°Black neon tetra 73–81°
The green band is the temperature range both can live in.
456789Both: 6–7.5Harlequin rasbora 6–7.5Black neon tetra 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Harlequin rasbora · 2 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

Harlequin rasboraBlack neon tetra
Temperature72–80 °F73–81 °F
pH6–7.55.5–7.5
Adult size2.0 in1.5 in
Minimum tank10 gal15 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for harlequin rasboras

All harlequin rasbora tank mates

Better tank mates for black neon tetras

All black neon tetra tank mates

Questions

Can harlequin rasboras live with black neon tetras?

Yes. Harlequin rasboras and black neon tetras get along in the same tank. Both are fine at 73–80°F. Plan on at least 15 gal.

What temperature suits both harlequin rasboras and black neon tetras?

73–80 °F. Harlequin rasboras need 72–80 °F, black neon tetras need 73–81 °F.

What size tank do harlequin rasboras and black neon tetras need together?

At least 15 gal, set by the black neon tetra. Add space for each extra fish.