During the first stages of fermentation, yeast requires lots of oxygen. Oxygen is removed from wort during the boil so it’s helpful to add oxygen back to the wort to ensure a healthy and complete fermentation. Yeast is more likely to have lower attenuation and produce off-flavors if there isn’t enough oxygen. To cut down on the lag phase between pitching the yeast and the onset of vigorous fermentation – aerate! Aeration system includes aerator pump, sanitary air filter and 2 micron diffusion stone. No assembly required! Carboy Not Included.