Personal experience, but I found coralline didn't grow as well under certain spectrums of LEDs. I had a tank near a window, and the side facing the sunlight was solid coralline, but the rest of the tank had the slightest sprinkling. That's why I added back T5s, as coralline used to be a pest for me. Kind of torn on which is better: lots or none.
If you have any of it in your tank, you don't need more, it'll be something it's missing, because as stated, it will grow like crazy if it's happy, even from the smallest speck. As suggested, if you have some on the glass, just scrape it and sprinkle it, although it's not necessary (the stuff 'spores' off like crazy).
