Well I have grown aquatic plants for years without co2 and am considering
giving it a try on my 50 or gallon tanks.  What i would like to know from
the experienced CO2 people is how much CO2 should I actually be adding to
the tank.

My initial idea is having a 2.5liter bottle under the stand with a regulator
on it.  What should i set the psi to?  then from the requlator I would run
it into air lines and probably 3 needle valves to control it going into
air stones and then simply sdjusting them for a small flow of bubbles.  Is 
this a viable idea?

Another thaught that I had was adding a siloniod valve to only alow CO2 in
my tanks when my lighs were on (usually about 9 hours a day on the 50 or
11 hours a day on my 80)  this should reduce my costs when the co2 is not
needed.  Is this a wise and viable idea as well?

Also what is the maintance cost on these systems?  How long does one of these
2.5 liter bottles last in a set up like i'm considering?

Thanks all.
Dennis                          mleather at tbdmil_com