I don't think the light plays a major role Scott. I have purple all over my sump, under rocks, everywhere, even where the light doesnt shine as bright. My opinion is it needs basic light and proper levels of calcium and other elements.
I've been messing around experimenting with my tanks over the last month as far as coralline growth. I have been adding purple up to my cube and my new 90g tank and both have shown a drastic increase of coralline growth since starting to use it. I have not put a drop in my 20g tank and there isn't a spot of coralline in the whole tank, except for on the rocks that originally had it.
Now, I'm not a big fan of adding chemcials to my tanks but I figured I'd give it a try. I used the regular dosage maybe 3 times a week for the last month and have noticed coralline growth within a day or so of each dosage. Maybe just me, maybe it actually can help,could be a coincidence but thought I'd throw it out there. LOL
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.