It doesn't look good but I have seen them come back from looking like this, believe it or not. Put it in a bowl with some rubble rock inside the tank in a low flow area where it will have little to nothing messing with it. Keep a watchful eye on it, if it starts to look like it's melting and your inverts are eating it, then it has died and you should remove it from the tank before it releases all of its stored up nutrients into the water.