Vampires got my hectors goby????

[naesco]

If it is skinny, it starve to death.
Getting them to feed and keeping them eating is the problem with Rainford, Hector and gobies of that species.

They need the same food as mandarins plus filamentous algae.

[christyf5]

Yikes that ain't good. The blue quality is because most of the skin (black) is gone and the very thin membrane between the skin and "meaty part" is bluish, your actinics may even accentuate it (if you have them). Likely he just didn't acclimate well to your tank

[Myka]

Did yours eat prepared foods? They don't usually eat prepared foods, and your tank being only 34g (if I remember correctly) likely would not provide enough food for him. They are big eaters. He probably starved to death. The condition he is in is simply from early decomposition, I doubt he was murdered.