i also agree with shanti... I just wanted to add that at one point in my dwc i had some pretty bad algae, and I used h2o2 to fix it... it worked ok, not great (wasn't using horticultural grade) but it did throw my PH way outta wack... I'd keep an eye on your ph if i were you... I would also say to use the horticultural grade, as I think it was buffers in the pharmy h2o2 that fucked my ph.
I researched this topic as well trying to find an answer, and read that algae isn't deadly (unless it's a massive outbreak of algae), so if it's more a PITA to treat the algae than live with it, i would just manage the algae when it comes up. Thats what I did, haven't used h2o2 since, and I'm already into flower w/no probs (the canopy tends to cover my DWC's, it should also adequately shield you nutrient solution ----> That is my speculation, tho.)