I have mine top dead center of the tank and what I really see with it is nutrients play the biggest role in the coloration for me.. When they are low the purple lightens up when they are a little higher I get the dark purple slap your mama coloration on it =)..
Low nutrients in my tank are higher than others reccomend though but just sharing what I see. Right now my tank is running at n03 =2-3 and p04. . 03-05..and that's low for me..
I completely agree with the above statement. Your coral is starving. Feed your tank more and or add more fish. Maybe feed coral food if you don't want to add more fish, but start slow so you don't get unwanted algae or red/brown slime. What is your stock list and tank size?
A lot of people believe that keeping NO3 and PO4 at zero are what you need to keep a successful sps tank. While it's good to start their your corals need to eat to survive and display their beautiful colors. Fish waste is the easiest way next is add coral food but you must find the right balance for your tank. I recommend starting at 1/4 or 1/2 the recommended dose see how your tank responds and go form there.
A lot of people believe that keeping NO3 and PO4 at zero are what you need to keep a successful sps tank
I personally think this is one of the worst trends to ever make it into the hobby(yet I'm tired of even saying it because it's like so frowned upon to even suggest anything higher to some people because they read it in an article so it has to be corrwct) along with the fear of algae.. If it grows there is something that will eat it imo.. Totally agree with akrite =)