If he was dead, and you have a good sized CUC, they would be all over him most likely. Id keep a CLOSE eye on it, as it WILL cause an ammonia spike when it goes.
It does look like its going, or about to go. Start testing for ammonia and watching to see if anything starts picking at him. If you see either, Id pull it out and give it a funeral. :-(
It could be expelling zooxanthellae (spelling?) rather than guts...