Can otocinclus live with swordtails?

Verdict
Yes

Yes, otocinclus and swordtails can live together. Both are fine at 72–79°F. Plan on at least 30 gal.

OtocinclusOtocinclus72–79°F · pH 6–7.5 SwordtailSwordtail72–79°F · pH 7–8.3

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 72–79°Otocinclus 72–79°Swordtail 72–79°
The green band is the temperature range both can live in.
456789Both: 7–7.5Otocinclus 6–7.5Swordtail 7–8.3
The green band is the pH both tolerate.

Size to scale

Otocinclus · 2 inSwordtail · 5 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

OtocinclusSwordtail
Temperature72–79 °F72–79 °F
pH6–7.57–8.3
Adult size2.0 in5.0 in
Minimum tank20 gal30 gal
TemperamentPeacefulSemi-aggressive
Swims atBottomMiddle
GroupGroups of 6+Groups of 3+
DietHerbivoreOmnivore

Better tank mates for otocinclus

All otocinclus tank mates

Better tank mates for swordtails

All swordtail tank mates

Questions

Can otocinclus live with swordtails?

Yes, otocinclus and swordtails can live together. Both are fine at 72–79°F. Plan on at least 30 gal.

What temperature suits both otocinclus and swordtails?

72–79 °F. Otocinclus need 72–79 °F, swordtails need 72–79 °F.

What size tank do otocinclus and swordtails need together?

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