Alexander was highly praised by Gregory Nazianzus (Or. 27) and Epiphanius of Cyprus (adv. Haer. lxix. 10). Theodoret called him an "apostolic" bishop (Hist. i. 3, cf. Phil. 12). In the commencement of the Arian troubles the co-operation of Alexander was specially requested by Alexander of Alexandria (Theod. i. 4); he was present at the First Council of Nicaea (Soz. ii. 29), in contrast to some beliefs of the attendance of the 117 years old bishop Metrophanes of Constantinople.
When emperor Constantine the Great, induced by the Eusebians (Athan Ep. ad Serap.; Rufinus, Hist. i.) and deceived by the equivocations of Arius (Socr i. 37), commanded that Arius should be received to communion, Alexander, though threatened by the Eusebians with deposition and banishment, persisted in his refusal to admit the archheretic to communion, and shut himself up in the church of Irene for prayer in this extremity. Alexander did not long survive Arius (Socr. ii. 6 ; Theod. i. 19). On his deathbed he was said to have designated Paulus as his successor, and warned his clergy against the speciousness of Macedonius.
Metrophanes of Byzantium
List of Constantinople patriarchs