What type of FL's are you using? Are they HO? I really like the set-up of your tank. It is awesome, I am just trying to get a feel for what you are using as that will help you out later. Since you want to use CO2, if you wanted to upgrade your lighting it wouldn't be detrimental after you implemented the CO2. But seeing as you are having problems with algae, I would hold off until after. Another thing is when figuring out lighting, its not the wattage you want to look at but the par value. This gives a better idea of how much light is getting to the plants. Another thing too look at with you fluorescence bulbs at the Kelvin temperature, if you haven't done so. 6500K is the min for plants, but ideally you want a mix 6500K - 10000K to get the most from your plants.
Another thing to look into is rooted tabs. Most people swear by them in regards to ferts. I personally use liquid as I have them and inject them into the substrate. As for the Excel, keep that up.
Again I love the look of your tank!