I'm sure I'm just repeating what others have said but and RO
solved my algae problems. (I was using conditioned tap water before and the algae was takng over). The difference now in my tank is enormous and the benefits of the RO
unit were almost instant. Highly recommended
I still get a tiny bit of green hairy algae (around my inflow pipe which my fish avoid) but it's nothing.
I never used any additives such as phospoban etc as I don't like adding formulas and chemicals to my tanks so i can't say whether that would help.
Reducing the light period did help a little (the algae growth slowed) but my leather coral didn't take kindly to it.
I also got a bicolour blenny who helped with algae control.
Hope the above helps - I had a large amount of cyanobacteria carpeting the tank with the hairy algae so you're problem may not be the same at all. But thought I'd post my experience anyway - might help.