[Delphinus]

Hi, wow, it's not that I don't beleive you Steve it's just that if those white areas are fleshy then the picture doesn't really show it that well. If that is flesh I think it looks awfully bleached.

I don't know if this helps, but, I basically have never been able to remove polyps off open brain skeletons for the reasons you've discovered. They just get too good of a foothold. If the zooanthid was more off to the side I'd suggest sacrificing that part of the brain and break the piece right off (that is the only sure way). But it's right in the center. You can try the kalk suggestion, but you run the risk of damaging the brain and losing both corals anyways.

My one last parting thought is this. Zooanthids are not overly aggressive to my knowledge. You can try to let the two corals live together and see what happens. Ideally, if they learn to live with each other they will just sort of grow around each other. Of course I have no idea how likely this is, I'm just guessing. That brain does look pretty far gone, it would be a nice pleasant surprise to see it recover to a full-out coral some day, but I'm not too sure I'd be placing any bets on it just yet anyways.

Sorry I couldn't be of better assistance! Good luck