I just recieved my first freshwater stingray today, I ordered him so he was shipped to my house, he is in pretty good shape. . . fat, no dent in his forehead but his belly doesnt look so good, kinda pink and some gray around the edges of his disc. Should I be concerned? Also he seems like he cant sit still on the bottom of the tank, kinda looks like he keeps floating up, any ideas on what is going on.