At this point, I dont think there is going to be much you are going to be able to do especially if you cant get him to eat.
QT/hospital tank is a must though.
White balance is a very important one in our hobby as the camera's don't like to photograph blue very well and the WB will help a lot with that. Saturation and Sharpness as well as f-stop and manual light metering are also used very often in photographing your tank and inhabitants.
well thats interesting, to clear it up the skeleton is still there exposed and just the tissue left as fly guy said. I did try to add 2 fish at the same time in my 30g, only one survived, so I bet that had something to do with it. Lesson learned.