I've had some Aussie Orange Zoas for a few months. It took them a few days to open up because they had been dipped before going into the DT. But, they did all open up regularly.
I'd noticed they weren't opening as often, and some polyps not at all. Started watching them and other zoas pretty closely, but all others are fine. No apparent predators, no cyano, and the zoas still look plump and healthy, just not open all the time.

Then I noticed a little greenish something growing. It's finally gotten big enough to get a pic.


What are these little hitchikers on the right? Can they be irritating the zoas?