Why is it so important to have the co2 in with the higher watts?

You need to have a balance: light, fertilizer, CO2. Increase one, and you must
increase the others, too, or plants won't grow well and algae will take over
(because of the extra light & nutrients the plants aren't using).

In addition, a high-light tank without CO2 injection can suffer large daily
swings in pH, as the plants strip the CO2 they need out of the water during the
day, then release CO2 back into the water at night.

Here are a couple of links at the Krib:

http://www.thekrib.com/Plants/balance-randall.html

http://www.thekrib.com/Plants/CO2/decalcification.html


Leigh

http://www.fortunecity.com/lavender/halloween/881/