CO2 injection/reactor

I'm still planning my next tank.  Given my budget, I have to stretch out
the planning process.

I will undoubtedly continue the DIY yeast CO2 with the next tank.  I can't
afford more at the moment, and besides, what's the big deal about mixing
sugar, water, baking soda, and yeast every so often?  AND I have nothing in
my home capable of becoming a ICBM.

I'm thinking about going with a 70 or 75 gal (suggestions welcome),
filtered with a Magnum 350 with biowheel.  Since I won't have a powerhead
anymore, I won't be able to hook my CO2 up to the air intake of the
powerhead.  My question:  if I go with bubblestones below the intake of the
Magnum, won't all the CO2 evaporate on the biowheel, with its large surface
area?  My dilemma:  I have no problem with putting together a reactor DIY
(if I can find the plans back), but I really would rather avoid something
big and ugly in my tank.

Thanks in advance,

Department of History
University of Iowa

P.S.   If anyone has any thoughts about the Magnum 350+biowheel 60 in terms
of its adequacy for the bioload of a 70 or 75 gallon tank, I would greatly
appreciate hearing from you.  I was taught that one filter/filtration
method was never enough, so the prospect of only having this seems really