That is an absolute beautiful fish, Bang.
I think Bang is right on this one.
What I have found that quickly controls algae within a couple of months is a properly built and maintained algae scrubber in combination with turning off lights for a week and adding a clean up crew that will munch on that specific algae.
But, as Bang pointed out, not all algae (such as Bryopsis) will not be eaten by a clean up crew.