Can siamese algae eaters live with upside down catfish?

Verdict
Yes

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

Siamese algae eaterSiamese algae eater75–79°F · pH 6.5–7.5 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°Siamese algae eater 75–79°Upside down catfish 72–79°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Siamese algae eater 6.5–7.5Upside down catfish 6–7.5
The green band is the pH both tolerate.

Size to scale

Siamese algae eater · 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

Siamese algae eaterUpside down catfish
Temperature75–79 °F72–79 °F
pH6.5–7.56–7.5
Adult size6.0 in4.0 in
Minimum tank30 gal30 gal
TemperamentPeacefulPeaceful
Swims atBottomBottom
GroupAlone or in pairsGroups of 3+
DietHerbivoreOmnivore

Better tank mates for siamese algae eaters

All siamese algae eater tank mates

Better tank mates for upside down catfish

All upside down catfish tank mates

Questions

Can siamese algae eaters live with upside down catfish?

Yes. Siamese algae eaters 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 siamese algae eaters and upside down catfish?

75–79 °F. Siamese algae eaters need 75–79 °F, upside down catfish need 72–79 °F.

What size tank do siamese algae eaters and upside down catfish need together?

At least 30 gal, set by the siamese algae eater. Add space for each extra fish.