Ball anemones are actually NPS corallimorphs. Based on those pics I think there's a good chance that's what they are.So story time, this tank was a pickup. I saw it on Facebook cheap and grabbed it. Guy said he hadn’t touched it in a year and it was fairly obvious that was true. I have found some coral alive still in here, and also a mushroom polyp. This seems anemone to me? But there are few of them. The 3-4 here and 2 on another rock. Always close together, never move.