light is more then just watts - PAR and spectrum as well as UV/actinic play an important roll in acclimation. "they" (don't ask me who they are or if "they" know what they're talking about) say thats it's easier for corals to go from higher light to lower light then in reverse. My personal experience is quite simple though - whenever i change an environment on a coral - i start it out on the very bottom of the tank and slowly move it to where i want it. in this way i have found i could put almost any coral under almost any light without too much stress. acclimation to a new environment takes a month at minimum. corals have to have time to allow their zoaxanthelea to adapt to the new light, hence the color shifts we notice. lighting will favor the growth of certain zoaxanthelea and the loss of others, we may notice this as bleaching. i killed an SPS once because i thought since it was coming from a tank that had much more light then mine i could just place it where i wanted it and it would be fine.... be mistake - it bleached and then RTNed in less then a week. i guess "they" don't really know what they're talking about
temperature is another factor in zoaxanthelea growth. i have found that my tanks higher summertime temps result in lighter corals and winter cools in darker.
stress is another factor, many corals shead zoaxanthelea in reaction to stress - any stress. example many of you know i'm fighting nudis in my fiji tank. after a fresh water dip many of my corals bleached a little - i could see they were sheading zoaxanthelea in their slime. i know it will take months before they come back to their full coloration. - d**n nudis!!!
sorry for the book - but bleaching is not a one liner....... many things fall into play. - patience, if all else is well they will color back up
