[1] He was possibly born in Lisbon, given that Iberian communities at the time usually chose their own citizens as bishops.
[2] Rodrigo da Cunha placed the first Christian communities in Lisbon between 36 and 106 AD and considered Potamius to be the fifth bishop (Mantius of Évora being the first), but this view failed to meet scientific rigor.
[2] In 318 or 319, Arius had founded Arianism, denying Trinitarianism by positing that Jesus' existence was not eternal and that his substance was not equal to that of God.
[2] Later, Arianism managed to regain some importance in the Roman Empire, mostly be the actions of Eusebius of Nicomedia and his (successful) attempts to exile the Nicean Athanasius of Alexandria.
[2] The Council of Sirmium in 357 strongly favored the anomoean trend, in line with the opinions of Ursacius, Valens, and Potemius.
[2] In fact, Potemius is reported to have played an important role in furthering Arianism in the 357 Council and in developing the pro-anomoean Second Formula of Sirmium that resulted from it.
[2] A book published in 383 or 384 (Libellus precum ad Imperatores) by Luciferians states that Potamius received a villa from Constantius II as a reward for his adoption of Arianism but then died as he made his way to it.