Ive heard so many method comparisons, pros and cons, and have tried them all but the fish pump. Ive settled with o2 injection and see no reason to ever change. The problem I see is that post boil the wort is depleated of o2. I dont have much faith in the headspace containing enough o2 to do the job. Splashing in open air might do it, but whats in the air? I just like my o2 wand. In my opinion its the surest and most sanitary method.