A freshwater trick when battling green cyano is to use antibiotics.
The antibiotic I used was called Erythromycin, it is generally sold to cure ick and other bacterial infections in you LFS.
From what I understand of it, cyano is actually more of a bacteria then algea. The antibiotic is not supposed to affect your benificial bacteria because they are generally a different type. Something about being gram positive while cyano is gram negative.
I have no idea if it a good idea in SW but it works like a mirical in FW. You could easily find lots of info on using it in fresh water with a quick google search. here is a link to a site I like.
http://www.thekrib.com/Plants/Algae/
Klick on Blue green algea (Cyanobacteria)
I would strongly recomend talking to some of the more experianced reefers before using it. Its a pretty common fix in FW so the fact that its not being used in SW kinda tells me that there is probably a reason.
Sorry about all the losses.
Jon