Can swordtails live with dwarf neon rainbowfish?

Verdict
Yes

Yes. Swordtails and dwarf neon rainbowfish get along in the same tank. Both are fine at 75–79°F. Plan on at least 30 gal.

SwordtailSwordtail72–79°F · pH 7–8.3 Dwarf neon rainbowfishDwarf neon rainbowfish75–82°F · pH 6.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–79°Swordtail 72–79°Dwarf neon rainbowfish 75–82°
The green band is the temperature range both can live in.
456789Both: 7–7.5Swordtail 7–8.3Dwarf neon rainbowfish 6.5–7.5
The green band is the pH both tolerate.

Size to scale

Swordtail · 5 inDwarf neon rainbowfish · 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

SwordtailDwarf neon rainbowfish
Temperature72–79 °F75–82 °F
pH7–8.36.5–7.5
Adult size5.0 in2.5 in
Minimum tank30 gal20 gal
TemperamentSemi-aggressivePeaceful
Swims atMiddleMiddle
GroupGroups of 3+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for swordtails

All swordtail tank mates

Better tank mates for dwarf neon rainbowfish

All dwarf neon rainbowfish tank mates

Questions

Can swordtails live with dwarf neon rainbowfish?

Yes. Swordtails and dwarf neon rainbowfish get along in the same tank. Both are fine at 75–79°F. Plan on at least 30 gal.

What temperature suits both swordtails and dwarf neon rainbowfish?

75–79 °F. Swordtails need 72–79 °F, dwarf neon rainbowfish need 75–82 °F.

What size tank do swordtails and dwarf neon rainbowfish need together?

At least 30 gal, set by the swordtail. Add space for each extra fish.