Zoas have been partially open for months. I set up a timelapse to see what was going on, because there were no visible irritants or pests. As you can see in the timelapse, the polyps seem to close up in response to flatworms crawling over them. I believe they are a type of acoel flatworm. There has been a population explosion since around the same time, like they’re visible crawling on the glass.
So what preys on acoel flatworms? They are so tiny I don’t know that a wrasse would be able to eat them.
So what preys on acoel flatworms? They are so tiny I don’t know that a wrasse would be able to eat them.