Some of coralline observations I've made over the years are
1. My tanks with the shimmer effect (halides & led
) have had much more aggressive growth vs my t5's and pc
's. I disagree with others that say light isn't a major factor since coralline grow underneath overhang etc. There is still light reflected of the substrate etc.
2. When I used c-balance from two little fishes as calcium / mag / stron supplement, I also had more aggressive growth vs other brands including purple up.
3. Also over the years, I've noticed more coralline growth when I have put my skimmers on a 12 hour on / off schedule, and an even larger increase when I installed a large refugium with micro algae and stopped skimming and using carbon all together.
4. And last but I feel my biggest observation was literally uncontrollable coralline growth when my nitrates and phosphates hit true zero in my latest tank with my large fuge with miracle mud and lots of micro algae competing for nitrates and phosphates.
These are just my experiences, but I'm sure others have gotten it other ways. I never seeded it in any of my tanks, and I had / have multiple colors as well.