Have had this zoa colony for about 9 months and growth has been excellent, but earlier today when I was watching my tank I saw some debris get ejected out of this gaping black hole in the colony that wasn't there yesterday. I assumed one of my emerald crabs ate its way inside the colony and so I shined a bright light into the hole looking for it but instead I found what looked like a mouth with a row of teeth, before the entire colony shifted downwards and the hole disappeared. Never seen anything like this before and I'm a bit concerned to say the least. I got 2 good pictures of the thing which I'll put in the comments.