That's the thing. I would never use Algaefix in an Acropora dominate system. If I had then I would more than likely change my rock out.
I prefer to not change out all of my established rock with tons of Acros if I don't really need to. What I want to know is if it is known to stay bound and could come out in the future. Probably hard to tell though given this is probably new to the field.
If it helps, my new tank is using about 20-25 pounds of rock that came from a tank very heavily dosed with Vibrant years ago.
These rocks have been covered in water for over 5 years now. They were the first to get hair algae in the new system. They also have SPS on them already. Knock on wood but I haven't lost a single coral in my transfer. I'm actually seeing growth on multiple SPS already. I credit the halides for that
BTW the ignore button is fantastic