I remember the days of chasing the coralline algae. It usually will come when you stop trying. No kidding. My current tank has been up for a couple years and up until about four months ago, it only had some on the live rock. Now I am scrapping constantly to keep it off the glass. I've been keeping reef tanks for about 15 years and this one usually comes down to patience. However, it is necessary to have something in the tank that has some on it. Lying in wait, until the conditions are right. Then, Bam! you will be buying some scrappers if you still want to be able to see into the tank. Good luck.