Re: "WW", O2, etc.

First of all, thanks to George and everyone else who have so patiently
explained this process.  I've kept planted tanks with various degrees of
success for decades, but other than occassional visits from Paul K. years
ago, I haven't had any contacts that really were familiar with the science

Perhaps you can help clear up a related misconception I may have been under: 

>With aereation, three things are happening.  The bubbles increase the
>surface area of the aquarium a little bit, allowing faster diffusion.
>They also expose some of the higher CO2 concentration areas in the
>water lower down to localized low concentrations (the CO2
>concentration in the bubble).  Most importantly, the turbulence allows
>the water to mix and keeps the water around the water/air interface
>supplied with higher concentrations, allowing diffision to occur at a
>more rapid rate.

Recent articles claim that the first two events involving reactions at the
water/bubble interface are now thought to be of very little significence -
at least as far as the addition of oxygen is concerned.  Does this also hold
true for CO2 exchange?  And if so, doesn't this mean that the circulation
caused by water pumps will be just as effective at "allowing diffusion to
occur at a more rapid rate"?  I've always been mystified as to why plant
books, including _The Optimum Aquarium_, denounce bubble-type aeration, yet
recommend "good circulation".  At first, I thought that perhaps the surface
tension of the water partialy blocked the exchange of gases, but then noted
such books also recommend surface agitation and even wet/dry filters.