I suppose it depends upon the aerator, but I can open a hole in 4" in just a few hours.
In my opinion, If you have no vegetation and the pond locks up, then I believe it would be a matter of how much O2 was present in the water, Vs. the biomass that depended upon it for survival, as to how long it could go before bad things began to happen. The first skim ice wouldn't bother me, but I personally see nothing wrong with aeration all through the winter, as long as you have shallow water diffusers.
"Forget pounds and ounces, I'm figuring displacement!"
If we accept that: MBG(+)FGSF(=)HBG(F1) And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1) Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT? PB answer: It depends.
