So am I looking for 1 to 1.5 watts per gallon??? The light above is 2 watts.
What are the different methods of CO2 incorporation to the tank?
Yes, Amstar, I believe you should be focusing on no more than 1 to 1.5 watts per gallon in a low tech tank.
While I agree with Assassin that wattage is really not the way to properly gauge & apply lighting for a tank, depending on what your overall objective is, wpg is nonetheless still a pretty good indicator of the way you should be heading to avoid an algea farm, and getting reasonable results, if that's the measurement you're used to in your marine environment.
Adding CO2, along with proper lighting & ferts, is a great enhancer to growing plants very well. While liquid carbon, like Seachem Excel, is good - it's quite expensive to use - whereas DIY yeast CO2 may be ok, but it's inaccurate in the main, and somewhat difficult to properly employ, with iffy results.
A pressurized CO2 system is the best, producing outstanding results if used properly, but is somewhat expensive to get started with. Do a little research, and determine what is best for yourself, given costs, size of tank, and expected results.