spleify! No coraline algae is not a bad thing, and from what I am understanding from what I have read, it is actually a good thing. For you will not get hair algea or red slime algae growing where coraline algae is present. As far as getting it to grow your lights should help that. For in my case I have only 3 colors pink, purple, and white. I would have to get a live rock with green on it and introduce that to the tank to get green to spread. I read if you want it to spread turn your pumps off for an hour and scrap some off and circulate it around the tank with power heads. That is the quikest way.