Candidianus was Patriarch of Grado (or New Aquileia) from 606 to 612, and the first with an opposing patriarch in Aquileia.
Venice had its own church organisation from the 800s, but the origins go back to before the Lombard invasion, and events in the Eastern Roman Empire.
The complete list of the Patriarchs of Grade, Patriarchs of Grado in Venice, and Patriarchs of Venice, since 717 until today