It’s definitely not going after any neighbors, it’s a 75g with a goniopora, a Rhodactis mushroom, an acro, leather coral, zoa and then itself. All spread out through the tank. There just kinda there, sticking out of the Duncan. They are all still frags too. Nobody is huge. Fairly new tank, 5 months maybe. It finished cycling March 19th.Not sure but it looks like some form of mesenterial filament. I have personally never known any of my Duncan’s to brother any neighbors.