I got this sea hare on Friday from my lfs to combat some hair algae I've been getting and today I came home to half it's body missing(the head half) and the bottom just floating by the sand bed. Now I saw him last night grazing and moving around so I have no idea what could have caused this. Is there any predators to it that I don't know about? And should I do a water change? I don't know if he inked or anything yet. I attached some photos so you can see what I mean.