Can swordtails live with hatchetfish?

Verdict
Yes

Yes, swordtails and hatchetfish can live together. Both are fine at 75–79°F. Plan on at least 30 gal.

SwordtailSwordtail72–79°F · pH 7–8.3 HatchetfishHatchetfish75–81°F · pH 5.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–79°Swordtail 72–79°Hatchetfish 75–81°
The green band is the temperature range both can live in.
456789Both: 7–7.5Swordtail 7–8.3Hatchetfish 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Swordtail · 5 inHatchetfish · 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

SwordtailHatchetfish
Temperature72–79 °F75–81 °F
pH7–8.35.5–7.5
Adult size5.0 in1.5 in
Minimum tank30 gal20 gal
TemperamentSemi-aggressivePeaceful
Swims atMiddleTop
GroupGroups of 3+Groups of 6+
DietOmnivoreCarnivore

Better tank mates for swordtails

All swordtail tank mates

Better tank mates for hatchetfish

All hatchetfish tank mates

Questions

Can swordtails live with hatchetfish?

Yes, swordtails and hatchetfish can live together. Both are fine at 75–79°F. Plan on at least 30 gal.

What temperature suits both swordtails and hatchetfish?

75–79 °F. Swordtails need 72–79 °F, hatchetfish need 75–81 °F.

What size tank do swordtails and hatchetfish need together?

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