writes:

wrong.. a great deal of air exchange occurs between the small air bubbles and the
water... those fine bubbles have a tremendous surface area and it not only puts air
(all the molecules of gases in air, not just oxygen) into the water,

Small bubbles have small amounts of air too.

I read an experiment decades ago in aquariums where bubbling air VS pure oxygen
was tried. Suprisingly, no difference in water O2 levels. It happens at the surface.

it lightens the
water and moves the water to the surface where it helps degas the CO2 and H2S and
other unwanted gases. think about sponge filters and how an airstone down inside
them creates enough of a suction that it pulls crap from the tank into and thru the
sponge. Ingrid

Yes, circulation and agitation are the keys.