Can fancy goldfish live with swordtails?

Verdict
No

No. Fancy goldfish and swordtails should not share a tank. Fancy goldfish are coldwater animals (65–74°F); swordtails need 72–79°F. They overlap only at 72–74°F, the edge of both ranges.

What to watch

What works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–74°Fancy goldfish 65–74°Swordtail 72–79°
The green band is the temperature range both can live in.
456789Both: 7–8Fancy goldfish 7–8Swordtail 7–8.3
The green band is the pH both tolerate.

Size to scale

Fancy goldfish · 6 inSwordtail · 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

Fancy goldfishSwordtail
Temperature65–74 °F72–79 °F
pH7–87–8.3
Adult size6.0 in5.0 in
Minimum tank30 gal30 gal
TemperamentPeacefulSemi-aggressive
Swims atAll levelsMiddle
GroupAlone or in pairsGroups of 3+
DietOmnivoreOmnivore

Better tank mates for fancy goldfish

All fancy goldfish tank mates

Better tank mates for swordtails

All swordtail tank mates

Questions

Can fancy goldfish live with swordtails?

No. Fancy goldfish and swordtails should not share a tank. Fancy goldfish are coldwater animals (65–74°F); swordtails need 72–79°F. They overlap only at 72–74°F, the edge of both ranges.

What temperature suits both fancy goldfish and swordtails?

72–74 °F. Fancy goldfish need 65–74 °F, swordtails need 72–79 °F.

What size tank do fancy goldfish and swordtails need together?

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