Originally Posted by exlfs
First, I assume that your Nitrates are where they should be, and that this is not simply a result of long-term exposure to poor water quality. I suspect, however that this is NOT the case, given your description of water quality parameters above.
This is TEXTBOOK Strontium deffeciency!
Without giving a 3 page description of the chemical relationship between alkalinity, pH, calcium, strontium and magnesium, I will just tell you that almost 100% of the time when an LPS coral releases itself from it's skeleton, there will be tell-tale signs that the tank is defficient in strontium or magnesium (most likely strontium). Think of Strontium as the "glue" which allows the coral polyp to keep attached to it's own skeleton. It's more complicated than that, but that's essentially the concept. So when LPS corals begin evacuating their skeletons, it's almost always due to a lack of one of these.....and usually the relationship between pH, calcium and alkalinity is out of balance as a direct result.
This is all assuming again that the coral was not damaged in some way, and that you have not experienced rapid spikes in tank temperature.
Best of luck and God bless....
The tank has not had any spikes in tank temperture as I use a chiller to keep my tank temp stable. Your right, it may be a sign of low strotium, but I have not added anythign that I cannt measure. So I decided to do bigger water changes and use real salt water until everything is back on track. And it looks like that is helping as the skin has grew back.