Maybe you got some pods crawling on them...irritating them. I know mine close like that when my pods hop all over them. I have a ton of them and my two clowns won't touch them.
I think there is a nudi (or some other very small organism) Crawling around their mat, disturbing their polyps, and causing the polyps to pulse and eventually close.
There is definitely some sort of Irritation going on.......I think. Reminds me, as it has been a while, to really gaze into my tank a while and watch. Might just learn something.
They may be feeding and each polyp is catching debris and exciting other polyps. They may also be irritated by something. I've seen this video before just can't remember what they were doing. That mushroom video is neat as well.
Purple Zoanthids - What do you think? 
Previous Thread
Next Thread
Linear Mode
