I can't comment on the CO2 setup because I don't use it. I can, however, tell you that rapidly growing floating plants seem to have a suppressive effect on algae as well. This seems to go beyond just shading the substrate. Since floating plants get as much CO2 as they need without CO2 supplementation, they grow very quickly, and may have a similar effect on algae growth to that of CO2.
My 40 gallon long tank is lit with 2 T5HO for eight hours per day, and has a large tiger lotus and a healthy Salvinia population. I fertilize with small amount of PMDD mix, and have almost zero algae woes. Nitrates are a steady 5-10 pmm, and phosphate is always undetectable.
I have seen floaters mentioned as algae control in discussions of Walstad style tanks. So, if pressurized CO2 isn't in the budget right now, maybe try some floaters. It may work for you like it did for me.