I don't know...just let it flow and grow on its own. Don't try to force anything on it I guess you can say. If you really want coraline, you can ask for some scrapings from a tank at your LFS and dump it in yours...that might boost it up.
My tank just started growing lettuce nudibranches out of nowhere...started with one and I named him Nudie...now I have nudie one and nudie two! :laugh: