Fluconazole works quickly on bryopsis, but takes longer with hair algae. I am just finishing 6 weeks with Fluconazole for gha. It seems gone. Just added extra phosguard, removed carbon, turned skimmer off, and kept up with filter sock changes. I did water changes and supplemented the Fluconazole in my water change so it wouldn't deplete. SPS, LPS, NPS, and softies are unharmed after 6 weeks.
I used 400mg Fluconazole in a 15 gallon system, and another 200mg in each 5 gallon water change. GHA is has not been visible anywhere since week 4, but leaving it longer to be sure.