Adapters and methods related to aeration applications. An adapter for use in water treatment applications. The adapter includes a generally circular member for conversion of an aeration diffuser holder from a membrane diffuser element holder to a ceramic diffuser element holder. The generally circular member includes a top adapted to receive a retaining ring, a bottom adapted to receive an aeration diffuser holder, a diameter adapted to receive a ceramic diffuser element, and a height adapted to receive a ceramic diffuser element.