On maricultured you really can't. They shouldn't be a problem at all. I have 3 maricutured acros in my tank, and all have at least one barnacle, and are healthy and growing well.
It's a barnacle, that's not the reason it's STNing
+1 barnacle. Common on wilds.
Yup, barnacles. Harmless creatures. Filter feeders.
I belive barnacles die off pretty fast in the aquarium.
Most probably, in my tank though, I have 3 or 4 that came on small frags (chopped up mari piece). Even 4-5 months later, they are still living as I can see movement. I guess it depends on how much and the quality of the liverock; as that may be producing enough foods for them in my tank.
As for the issue with the coral itself, is this a maricultured coral? How long have you had it in your tank?
Are you certain all other corals are fine?
Your photos are very good. I cannot see any AEFW bite marks. So, at least that is a relief. Have you basted the coral in just tank water in a separate container?
My LFS had one maricultured piece that had the same issue you are having. They then fragged it up. Some of the frags health over, some continued to have the same issue you are having and I saw the frags a few days ago, those ones that looked bad are are dead.
I bought one of the frags that looked better than most. For a while in my tank it was OK. But its been more some weeks and I can see it has areas which look identical to yours.
All the other acros in my tank are fine and growing nicely. All my parameters check out nicely. Tank is coming up to 9 months, having been setup with rock from a previous setup.
If this is a mari piece then that might explain it to some extent. Some mari pieces are just like that. Maybe the flow or maybe the food is insufficient.
