Any ideas on why this coral is dying?

[darth reefer]

Attached is a pic of a green Psammocora from my tank. Two days ago I noticed a white spot on its side that is progressing very quickly. It almost looks like it is rotting and falling away from the skeleton. It has been in my tank for almost a year and has always been a very slow but steady grower. All of my other sps looks great. There have been no changes made to the tank and parameters have been steady as always. Really scratching my head on this one. Any ideas?
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[kzoo]

Any other corals touch it?

 

[darth reefer]

Nope, nothing is anywhere near it.

 

[no1bubba]

I have the same coral and the exact same thing is happening. And like yours, nothing is near it. Just started last Monday. Bubba

 

[softhammer]

How about the fact that the receding area is shaded? Happens to almost any coral and should stop once hitting the better lit parts...Hopefully!

 

[containerman1]

If it were me I would check Alk. make sure its correct and I would remove the coral and put a little reef dip / iodine on that spot let it sit for a min. and add back to tank.
It has worked for me a few times on spots that looked similar

 

[darth reefer]

Yeah I was thinking the same thing about the shaded areas. The spots are spreading everywhere and while yes they are all in shaded areas I have seen the mother colony this frag came from and it doesn't have any dead spots like this. My alk stays rock steady at 8.9dKH. I would try to take it out but the base is fully encrusted on a lare rock in the middle of my aquascaping. Really don't want to tear it all down. Thanks for the tip though! I will remember it in the future.

 

[no1bubba]

in my case, there is not shade but by alk is a little low, started to bring it back up today. Will try the reef dip in the morning. Thanks, Bubba