One of my oldest '"reef tanks" ,which was started with crappy cheap as* L.R. over one year ago, still has very little coraline growth on rocks (although I've spent hours scraping pink coraline off glass in same tank)! This 37g tank runs{2}55/65w pc. In other tanks, I have awsome coraline growth on L.R. due to several things(I belive).1:Tanks were stocked with average quality L.R. (AND) pieces of high quality prime L.R.(to help seed the rest)2:More light (although most coralines do not require/prefer bright lighting).3:good circulation. Think of coraline algae as a "plant", and you are the gardener. In order for you to produce a good garden, first you must sew your seed's(introduce multiple strains of coraline through multiple sources). Provide your garden with a good environment (light,calcium etc.),...and before you know it, your garden will flourish (and you will have earned your "purple" thumb)!