GSP won't open

[pseudorand]

My green star polyps won't open. I noticed it yesterday and assumed a crab or urchin or something had just walked over the. But they're the same way this evening, and it's earlier than they usually retreat, so I suspect they're been that way all day.

Nothing else in the tank seems unhappy. I did do a water change yesterday and the new water does flow right towards them, but I know temp and salinity we're spot on.

I only ever heard they're impossible to get rid of, never that they're suspectable to anything the wouldn't affect my other corals first.

Any ideas? If I figure it out, I'll be sure to post here for those who want to be rid of theirs.

This colon started on a single, small frag plug less than a year ago and had been going gangbusters until yesterday (as expected for GSP).

 

[blaxsun]

I'd give it a few days. They will often close up for no apparent reason to encourage scavengers to clean them, etc.