I have a GHA farm. I believe mine was caused by old RODI filters, feeding nothing but flake/pellets, and poor maintenance. I tried all the animal treatments; turbos, sea hair, pencil urchin, lawnmower with no real luck. I changed my filters, reduced the flake/pellet feeding, and started manually removing a ton. Then I added a phosphate reactor(actually a Bulk Reef Supply two canister GFO/GAC unit) and this has helped the most. You might look into getting a Two Little Fishies reactor and see what that does for you.

I was ready to use the Algae FX marine as people on RC seem to be having a lot of work with it. But my reactor started limiting it's growth and I'm happy that I don't have to use chemical warfare.