Purple Nana Color Change

[Aquattro]

Tony, keep in mind that switching color temp bulbs also results in changes of PAR values. A 400w 65k is a LOT brighter than a 400w 20k bulb.
Just a note also, brown (poo) may be the natural(healthy) color of that coral. Purple may be a defense to the properties of the previous light.

And on the Radiums, I wouldn't recommend them if you're only desiring a color change in corals. I have to say that I don't have any net change in my tank after switching; some got a bit nicer, some got a bit not nicer(lost for words there!!). I still prefer the look of the Radiums for my viewing pleasure, but they didn't transform my tank to colorworld!!