Can discus live with harlequin rasboras?

Verdict
No

No. Discus and harlequin rasboras should not share a tank. No shared temperature. Discus need 82–88°F, harlequin rasboras need 72–80°F.

DiscusDiscus82–88°F · pH 5.5–7 Harlequin rasboraHarlequin rasbora72–80°F · pH 6–7.5

What to watch

What works

Water side by side

55°60°65°70°75°80°85°90°Discus 82–88°Harlequin rasbora 72–80°
The ranges do not meet, so one of them would always be too warm or too cold.
456789Both: 6–7Discus 5.5–7Harlequin rasbora 6–7.5
The green band is the pH both tolerate.

Size to scale

Discus · 6 inHarlequin rasbora · 2 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

DiscusHarlequin rasbora
Temperature82–88 °F72–80 °F
pH5.5–76–7.5
Adult size6.0 in2.0 in
Minimum tank55 gal10 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 5+Groups of 6+
DietCarnivoreOmnivore

Better tank mates for discus

All discus tank mates

Better tank mates for harlequin rasboras

All harlequin rasbora tank mates

Questions

Can discus live with harlequin rasboras?

No. Discus and harlequin rasboras should not share a tank. No shared temperature. Discus need 82–88°F, harlequin rasboras need 72–80°F.

What temperature suits both discus and harlequin rasboras?

None. Discus need 82–88 °F and harlequin rasboras need 72–80 °F, so the ranges do not meet.

What size tank do discus and harlequin rasboras need together?

At least 55 gal, set by the discus. Add space for each extra fish.