Can fancy goldfish live with ember tetras?

Verdict
No

No. Fancy goldfish and ember tetras should not share a tank. Fancy goldfish are coldwater animals (65–74°F); ember tetras need 73–84°F. They overlap only at 73–74°F, the edge of both ranges.

What to watch

Water side by side

55°60°65°70°75°80°85°90°Both: 73–74°Fancy goldfish 65–74°Ember tetra 73–84°
The green band is the temperature range both can live in.
456789Both: 7Fancy goldfish 7–8Ember tetra 5.5–7
The green band is the pH both tolerate.

Size to scale

Fancy goldfish · 6 inEmber tetra · 0.8 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 goldfishEmber tetra
Temperature65–74 °F73–84 °F
pH7–85.5–7
Adult size6.0 in0.8 in
Minimum tank30 gal5 gal
TemperamentPeacefulPeaceful
Swims atAll levelsMiddle
GroupAlone or in pairsGroups of 6+
DietOmnivoreOmnivore

Better tank mates for fancy goldfish

All fancy goldfish tank mates

Better tank mates for ember tetras

All ember tetra tank mates

Questions

Can fancy goldfish live with ember tetras?

No. Fancy goldfish and ember tetras should not share a tank. Fancy goldfish are coldwater animals (65–74°F); ember tetras need 73–84°F. They overlap only at 73–74°F, the edge of both ranges.

What temperature suits both fancy goldfish and ember tetras?

73–74 °F. Fancy goldfish need 65–74 °F, ember tetras need 73–84 °F.

What size tank do fancy goldfish and ember tetras need together?

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