Yes, Otocinclus, commonly known as Otos, are social and do best in groups. These small catfish are strongly herd oriented and prefer living in schools of their own kind. Keeping them in groups enhances their sense of security and can significantly decrease stress, leading to better overall health and longevity.
Aquarists advise maintaining a group of at least three to six Otos. However, keep in mind that each Oto requires adequate space. The more, the merrier is the general rule with these little algae eaters, but the size of the tank should be the ultimate determinant of the group size.