Together with Bishop of Lucca Anselmo da Baggio (later Pope Alexander II), Arialdo headed the pataria, a movement that sought to reform Milan's simoniacal clergy. Due to this, he was excommunicated by the Bishop of Milan Guido da Velate. Pope Stephen IX removed the excommunication and Arialdo returned to Milan to continue his efforts towards reformation.
Arialdo, along with Bishop of Lucca Anselmo da Baggio (who later became Pope Alexander II), led the pataria movement that sought to reform Milan's simoniacal clergy. This resulted in his excommunication by the Bishop of Milan Guido da Velate. However, Pope Stephen IX lifted the excommunication and Arialdo returned to Milan to continue his efforts toward reformation.