JennM;601017 wrote: Return it.
No one in their right mind should have sold this fish to you if they were aware it was going in a 14 g tank (or any tank under about 75 gallons.)
This is *not* a goby (although 90% of the industry refers to it as such) it is a dragonet. As others mentioned, it is unlikely to accept prepared foods and lives on tiny arthropods that occur in the tank. In such a small tank it will eat these tiny crustaceans, much more quickly than they can reproduce, and as such, the fish will slowly starve to death.
No they do not "molt", so if your fish is sloughing skin, something is dreadfully wrong. Either it arrived sick, or something in your tank's water quality is not suitable. What are your parameters?
Jenn