Can firemouth cichlids live with upside down catfish?

Verdict
Yes

Yes. Firemouth cichlids and upside down catfish make a good pair. Both are fine at 75–79°F. Plan on at least 30 gal.

Firemouth cichlidFiremouth cichlid75–86°F · pH 6.5–8 Upside down catfishUpside down catfish72–79°F · pH 6–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–79°Firemouth cichlid 75–86°Upside down catfish 72–79°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Firemouth cichlid 6.5–8Upside down catfish 6–7.5
The green band is the pH both tolerate.

Size to scale

Firemouth cichlid · 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

Firemouth cichlidUpside down catfish
Temperature75–86 °F72–79 °F
pH6.5–86–7.5
Adult size6.0 in4.0 in
Minimum tank30 gal30 gal
TemperamentSemi-aggressivePeaceful
Swims atBottomBottom
GroupAlone or in pairsGroups of 3+
DietOmnivoreOmnivore

Better tank mates for firemouth cichlids

All firemouth cichlid tank mates

Better tank mates for upside down catfish

All upside down catfish tank mates

Questions

Can firemouth cichlids live with upside down catfish?

Yes. Firemouth cichlids and upside down catfish make a good pair. Both are fine at 75–79°F. Plan on at least 30 gal.

What temperature suits both firemouth cichlids and upside down catfish?

75–79 °F. Firemouth cichlids need 75–86 °F, upside down catfish need 72–79 °F.

What size tank do firemouth cichlids and upside down catfish need together?

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