According to Gelasius of Cyzicus, Metrophanes was alive during the First Council of Nicaea (325), but could not partake due to his age and ill health, so he sent instead Alexander of Constantinople, whom he destined as his successor.

[9] Alexander served as bishop for about 23 years,[10] during which time he distinguished himself by his virtues and administrative abilities.

The Roman Emperor Constantine the Great, having been convinced by the Eusebians, commanded Alexander to formally receive Arius back.

[13] According to Socrates of Constantinople, Arius did not in fact repent of his heresy but was equivocating, and Bishop Alexander was aware of this.

[14] Alexander, though threatened by the Eusebians with deposition and banishment, persisted in his refusal to admit Arius back into the Church, and shut himself up in the Church of Hagia Irene (which at that time was the cathedral of Constantinople) in fervent prayer that God would take him from this world rather than be forced to restore someone to communion who he feared was only feigning repentance.