Water flow plays a huge part in the kind of algae that grows. If there is not enough water flow or a lot of dead spots in the tank, nuissance algaes like hair and slime will go crazy. The waste in a tank builds up on the bottom and the rocks in still areas of the tank and the nitrates and phosphates feed the algaes. With good water flow around and through the rocks and substrate, the waste doesn't settle, at least not as much, and the nuissance algaes don't take as strong a hold. Also keep the rocks blown off of anything that does settle on it. With proper water chemistry and lighting, this alows the coralline to take off. I never had to scrape mine to spread the coralline because the LR I have had a decent amount to start, and once my tank parameters became constantly good the stuff spread everywhere in a short time. Now I have to scrape the glass all the time and it seems to spread overnight. A lot of the guys and girls on here have more experience and knowledge than me, these are just my observations in my 7 plus months with my reef. I've learned more on this site from others' experiences than I ever could have by reading alone.