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