Can hillstream loaches live with otocinclus?

Verdict
Yes

Yes. Hillstream loaches and otocinclus get along in the same tank. Both are fine at 72–75°F. Plan on at least 20 gal.

Hillstream loachHillstream loach68–75°F · pH 6.5–7.5 OtocinclusOtocinclus72–79°F · pH 6–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–75°Hillstream loach 68–75°Otocinclus 72–79°
The green band is the temperature range both can live in.
456789Both: 6.5–7.5Hillstream loach 6.5–7.5Otocinclus 6–7.5
The green band is the pH both tolerate.

Size to scale

Hillstream loach · 2.5 inOtocinclus · 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

Hillstream loachOtocinclus
Temperature68–75 °F72–79 °F
pH6.5–7.56–7.5
Adult size2.5 in2.0 in
Minimum tank20 gal20 gal
TemperamentPeacefulPeaceful
Swims atBottomBottom
GroupGroups of 3+Groups of 6+
DietHerbivoreHerbivore

Better tank mates for hillstream loaches

All hillstream loach tank mates

Better tank mates for otocinclus

All otocinclus tank mates

Questions

Can hillstream loaches live with otocinclus?

Yes. Hillstream loaches and otocinclus get along in the same tank. Both are fine at 72–75°F. Plan on at least 20 gal.

What temperature suits both hillstream loaches and otocinclus?

72–75 °F. Hillstream loaches need 68–75 °F, otocinclus need 72–79 °F.

What size tank do hillstream loaches and otocinclus need together?

At least 20 gal, set by the hillstream loach. Add space for each extra fish.