Okay, Zooxanthellae is the algae lives in a coral and provides most of it's food from light...This is why light is so important in a reef tank. The extra food that the Zooxanthellae produce is taken up by the coral. If the temp. or in my case the ALK level does not suit the algae they can die. This leave the coral without the color of the algae and it's food supply and in most cases the Coral dies. This is called "Bleaching".Um i have no idea what you just said Thincat but it sounded interesting lol!