A hollow expansion chamber of the present invention is configured to temporarily contain an expansion of bubbles during an aeration process for aerating a liquid, where a chamber body of the expansion chamber has an oblate spheroid shape. When moving circumferentially downward along the chamber body starting from a maximum inside diameter, the oblate spheroidal shape of a bottom portion has a first integral transition that is a tangential transition to a first frustoconical shape. Continuing moving circumferentially downward, the first frustoconical shape has a second integral transition to a cylindrical extension. The cylindrical extension at a distal end has a bottom opening configured to fit within an opened bottleneck. The first frustoconical shape has a minimum angle of 15 degrees relative to a horizontal plane. The second integral transition is a radial second integral transition having an inside surface radius of at least 0.25 inches.