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CO2 required for brightly lit tanks?

	Some people seem to believe that CO2 injection is a requirement
for a brightly-lit tank.  This notion is based on the quite reasonable
assumption that with enough light (say, more than 2.5 Watts per gallon),
the plants are trying to photsynthesize too rapidly for the level of CO2
normally available in a non-CO2-injected tank.  Thus, there is an
imbalance, and various attendant problems.  However, I have also seen
claims, some from dr. dave in his refreshingly blunt fashion ;-), that in
most/many situations, CO2 injection is not necessary.  These claims say
that in effect, we can compensate for lower levels of CO2 by, well, let's
call it,"making CO2 more accessible."  So, instead of getting more CO2 to
the plants by increasing CO2 concentration in the tank via CO2 injection,
we work with the CO2 levels we have, and simply make it easier for the CO2
to be taken up by the plants.  Plants have a boundary around their leaves
(Prandtl boundary) which makes it difficult for gasses, such as CO2, to
diffuse through.  (Why do they have this boundary, btw, if it actually
makes it more difficult to access CO2? dave?)  What we aquarists can do,
is disturb this boundary with a good current, thus making it easier for
CO2 to diffuse through.  Hence, something like a good powerhead blowing
through our miniature jungle, can solve our problem.  "Or, we can even
employ a bubble wand or something of that nature.  True, the bubble wand
will perhaps lower the CO2 concentration (if the tank is heavily populated
enough with fish to have a CO2 concentration higher than its natural
equilibrium with the atmosphere), but the increased diffusion rates more
than compensate.
	Now, the above is meant to be only a summary of what is actually a
wonderfully complex process, but I hope so far I have not made any basic
errors in fact or theory, since my question assumes the above is
essentially correct.

	I have a 20 long that I plan to convert into a lushly planted
tank.  (Once I get the pink gravel out of there ;-) ....don't ask). Given
that the tank is fairly shallow (12", I believe), do my fellow APDers
think I would run into trouble w/out CO2 injection if I were to install a
hood, painted white on the inside, w/ a total of 70 watts of T-8 lamps?
These would be two 2' 18w 6500K, and two 2' 17w 4100K or 5000K.  I was
hoping to simply use a good current via a powerhead to blow across plants,
plus keep the Aquaclear 200 currently filtering the tank.  How about with
one lamps less, for a total of 52/53 w?  Oh, and I should also mention
that I plan to have floating plants as well, probably Salvinia.