Coraline can be a pain to clean off the glass but it is good for the system. It works as a nutrient export as any other algae does. Yes it uses Ca, but that is out weighed by the benifits. I don't think it needs real strong lighting but does benifit from high Kh. I have it growing faster in my fuge with just a 23w cf daylight bulb from Homedepot than in my tank with 720w of light. You can use a razor to clean off the glass and even scrape some off your rocks to help it spread faster. I have been using 2 part for a long time with good coraline growth. I just set up a Ca reactor so I will see if it improves.