From experience I've had with algae and advise I got from other members here on RB, I would worry more about getting the water parms in check, if possible cut the lights for a few days. Once the nitrates and phosphates are in check that will starve the algae and it will start going away slowly on it's own.
If you're overfeeding cut back. Make sure your bulbs are OK, could try something like Pura Phoslock or Phosban.
I know you said you're using RO water, is it a RODI unit? if not consider adding DI.
After about 6 months my TDS meter was still reading "0" TDS and I had a crazy algae bloom...I got sick of trying almost every thing and replaced my RO filters...not sure if it's coincidence but the algae problem went away on it's own.
I've asked the question many times "does 0 TDS mean your water is OK?" I've read lots of articles, maybe I'm just stupid but I can't seem to get the "Yes" or "No" answer I'm after...It's like going to the Dr. they could never give a straight answer
Good luck