Wort or Must Aeration Methods
Yeast requires oxygen during the respiratory phase. Without oxygen yeast cannot reproduce and create a colony large enough for a vigorous, complete fermentation. Insufficient oxygen during the respiratory phase can result in a slow, sluggish or incomplete fermentation with the yeast potentially becoming stressed and diverting to side paths resulting in off characteristics. So it is important to adequately aerate your wort/must. Wort aeration should always be done after the wort is cooled because aerating hot wort has the potential to cause problems. After fermentation begins, oxygen should be excluded from the process.
There are various ways to aerate cooled wort or must. Vigorous splashing by dribbling the wort or must into the fermenter or stirring will add some oxygen. It is relatively ineffective, but better than nothing.
Using a Mix-Stir attached to a drill is moderately effective especially if it is repeated several times as the foam generated by the mix-stir subsides.
An aquarium pump with a stone and .2 micron inline filter does a better job. It is reasonably effective except for high gravity worts or musts.
The most effective method of dissolving oxygen in solution is with a pure oxygen tank with a regulator and stone. This is the way it is done by commercial breweries.