Many things have been thought to account for the coral tissue pulling away from the skeleton, Hanna. Often it is attributed to stress, disease, and/or improper water conditions (typically low calcium or alkalinity), but there are quite a number of ideas floating around for what could cause this condition among scleractinian corals in the aquarium.
Eric Borneman & Jonathon Lowrie discuss coral disease and immunity in some detail in Part 1 and Part 2of their article on the Immune Response of Corals in the Aquarium.Net archives, and I believe that Eric has a section on coral problems in his book Aquarium Corals. I know he also discusses it in a talk he gave for Reefs.Org a while back...
If this is not really what you were looking for, let me know, or you might want to post a more specific question for Eric on his coral forum...
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Hanna:
<strong>What causes the flesh to leave the skeleton? Hanna. [email protected]</strong><hr></blockquote>
In addition to the possible causal factors that Rob mentioned, high phosphate can also (apparently) cause corals to receed from their skeletons.
