I think that the question of how, and how much, to aerate is dependent on too many variables to specify a "best" method or time.
As previously stated, oxygen is only needed in the growth stage of yeast. The only reason to oxygenate wort is when yeast is pitched at a lower cell count than necessary for the quantity of wort being fermented. In theory, if the yeast has been previously oxygenated in the process of making a starter, and has been built up to a sufficient cell count, there should be no need to aerate the wort at all. Fermentation takes place anaerobically. Dry yeasts, in particular, have been through the whole growth stage and, as long as the viable cell count is high enough, they should be good to go without any further oxygen.
I had personally been plagued with sluggish and, at times, high FG fermentations back when I was using pure oxygen for aeration. Once, I even had a beer judge comment that my beer was oxidized, and it was only 6 weeks old! I then switched to a an aquarium pump, and noticed an immediate improvement in fermentation times and FG's. I believe, under the right conditions, that aeration of wort is not necessary and can, in fact, be detrimental.
I will be brewing in the next week or two, and I am going to put my theory to further test. I will pitch two packs of US-05 in a 5 gal. batch. The only aeration it will receive is whatever splashing occurs as it is transferred into the fermenter and moved.
As previously stated, oxygen is only needed in the growth stage of yeast. The only reason to oxygenate wort is when yeast is pitched at a lower cell count than necessary for the quantity of wort being fermented. In theory, if the yeast has been previously oxygenated in the process of making a starter, and has been built up to a sufficient cell count, there should be no need to aerate the wort at all. Fermentation takes place anaerobically. Dry yeasts, in particular, have been through the whole growth stage and, as long as the viable cell count is high enough, they should be good to go without any further oxygen.
I had personally been plagued with sluggish and, at times, high FG fermentations back when I was using pure oxygen for aeration. Once, I even had a beer judge comment that my beer was oxidized, and it was only 6 weeks old! I then switched to a an aquarium pump, and noticed an immediate improvement in fermentation times and FG's. I believe, under the right conditions, that aeration of wort is not necessary and can, in fact, be detrimental.
I will be brewing in the next week or two, and I am going to put my theory to further test. I will pitch two packs of US-05 in a 5 gal. batch. The only aeration it will receive is whatever splashing occurs as it is transferred into the fermenter and moved.