coral dying?
 

Forgive me in advance for my lack of terminology!

I got home last night and a coral in my tank looks horrible. All other corals are doing great all open extended and such. But this coral was shrunken and turned from yellow to a greenish color. It's usually fluffy and has a bunch of polyp (I don't even know if that's the word I am looking for) like things comin out of it.

Nothing in the tank has changed, nothing new has been added. It is usually the size of a toonie and now it's between a nickle and a quater.

I. Don't have a pic of it when it is open... But I have a full tank shot that you can see it dead center under the clam!

Hard to tell from the pic, but if that's a sarcophyton or leather coral, as long as your water parameters are good, it is normal behaviour for that type of coral. It sometimes will shrink and shed a protective mucous layer.
Make sure that you have alternating water flow around it and all other corals.
That type of coral releases toxins that are harmful to other corals.
Have some activated carbon running to help absorb those toxins.

Examine the coral to see if you can see any areas that look rotten or are dissolving away. In that case, the coral is sick and you may need to cut off a healthy area in order to regrow it elsewhere.

Mitch

It just looks closed up to me. How long have you owned it?

+1 It is normal for leathers to do this.

I have had it for about a year and have never noticed it do this before. I am going home right now! I'll give an update soon!