I had to cut back on my feeding, and lights. Then suck as much of it out as possible and direct a strong current at it. It took about 4 months to completely get rid of it.
It feeds off of nitrates so cuttomg back on feeding will help, but I believe it will also create its own nitrate. That's why I say suck as much out as possible to cut back on its food supply.
Once my system began going through the briopsis and cyano stage I cut back drastically on the display lighting but boosted the lighting schedule in my refugium. Basically running about one day of light (maybe 2-4 hours) for every two days of darkness. After about a week or two the briopsis and or cyano took off like a rocket in the refugium and virtually disappeared from the display. Been that way ever since.
If ever I see it trying to creep back up in the display I automatically cut the lighting schedule for a day or two and reduce feeding for a bit. Seems to work like a charm and no hand maintenance. Thx, beaslbob!