A method and apparati for regulating introduction of ambient air begins with initiating a liquid flow through a venturi to induce a localized drop in pressure at a bowl situated at a venturi throat. Airflow is admitted at a barrel inlet, through a first barrel lumen segment to a first half-moon port at a throttle first side. The airflow is selectively obstructed by a second half-moon port whose rotational position relative to the first half-moon port defines a variable aperture. The airflow is conducted from the second half-moon port through a second barrel lumen segment to the barrel outlet and mixing with the liquid to produce an aerated liquid.
