I have macroalgae (halimeda) growing on and in between my rockwork (they came on the lr). When I first got the rocks the macroalgae wasn't looking so good and I figured it was a goner and ignored it. A few days later new stems and leaves started appear all over and now it looks really great. In fact, I wish I had more of it.
Every few days I see new leaves popping out of the rockwork. My hermit crabs seem to like it and take it upon themselves to trim it before it gets too long, thus keeping the growth in check but w/o impeding the health or growth of the macroalgae.
All in all, I love it and wouldn't change a thing.