Can fancy goldfish live with rummy nose tetras?

Verdict
No

No. Fancy goldfish and rummy nose tetras should not share a tank. Fancy goldfish are coldwater animals (65–74°F); rummy nose tetras need 75–84°F. No temperature suits both.

What to watch

Water side by side

55°60°65°70°75°80°85°90°Fancy goldfish 65–74°Rummy nose tetra 75–84°
The ranges do not meet, so one of them would always be too warm or too cold.
456789Both: 7Fancy goldfish 7–8Rummy nose tetra 5.5–7
The green band is the pH both tolerate.

Size to scale

Fancy goldfish · 6 inRummy nose tetra · 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

Fancy goldfishRummy nose tetra
Temperature65–74 °F75–84 °F
pH7–85.5–7
Adult size6.0 in2.0 in
Minimum tank30 gal20 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 rummy nose tetras

All rummy nose tetra tank mates

Questions

Can fancy goldfish live with rummy nose tetras?

No. Fancy goldfish and rummy nose tetras should not share a tank. Fancy goldfish are coldwater animals (65–74°F); rummy nose tetras need 75–84°F. No temperature suits both.

What temperature suits both fancy goldfish and rummy nose tetras?

None. Fancy goldfish need 65–74 °F and rummy nose tetras need 75–84 °F, so the ranges do not meet.

What size tank do fancy goldfish and rummy nose tetras need together?

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