I know and I keep hearing that. Even tho my tank was free, nothing else has been and I had nothing to start with. So adding co2 right now is not in the cards (nor in the wallet). In addition, I'm not sure I want to add the complexity of the whole pressurized thing...right now. Part of my goal with this tank is to provide me with an outlet for my tendencies to fiddle with things and so I can see co2 in the future.
Soon as my orchids get outside, I'll probably go to 250w by taking my CFL's off the orchids and onto the tank. Then I WILL add co2.
The other problem, naturally, is adding the 125g that a friend has for me. That has filter, tank, stand and gravel. On that one, I'm going to start slower and make it fully planted from the get-go. It will have co2 from the start.
Anyway, this one, for now, is just going to get excel. Last night was the first dosing of comprehensive and (unless it's my imagination) the plants already look better!