Can fancy goldfish live with upside down catfish?

Verdict
No

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

Fancy goldfishFancy goldfish65–74°F · pH 7–8 Upside down catfishUpside down catfish72–79°F · pH 6–7.5

What to watch

What works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–74°Fancy goldfish 65–74°Upside down catfish 72–79°
The green band is the temperature range both can live in.
456789Both: 7–7.5Fancy goldfish 7–8Upside down catfish 6–7.5
The green band is the pH both tolerate.

Size to scale

Fancy goldfish · 6 inUpside down catfish · 4 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 goldfishUpside down catfish
Temperature65–74 °F72–79 °F
pH7–86–7.5
Adult size6.0 in4.0 in
Minimum tank30 gal30 gal
TemperamentPeacefulPeaceful
Swims atAll levelsBottom
GroupAlone or in pairsGroups of 3+
DietOmnivoreOmnivore

Better tank mates for fancy goldfish

All fancy goldfish tank mates

Better tank mates for upside down catfish

All upside down catfish tank mates

Questions

Can fancy goldfish live with upside down catfish?

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

What temperature suits both fancy goldfish and upside down catfish?

72–74 °F. Fancy goldfish need 65–74 °F, upside down catfish need 72–79 °F.

What size tank do fancy goldfish and upside down catfish need together?

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