get a cocktail shrimp and dip it in garlic oil.. then throw it in the tank. that's the last ditch effort
however, he will probably not eat until he gets into some brackish water... which is why the people here are stressing that you get the water taken care of ASAP.
the behavior is a result of the environment, until you change the environment, the behavior will probably not change... certainly not permanently.
and your LFS stores are correct.. there is no such thing as a freshwater snowflake eel. there is no such thing as a true freshwater eel. period. they are all brackish and must have brackish water and eventually full salt water. however, when they're young that can survive in freshwater for a short period of time, and this is (unfortunately) when they are sold as freshwater eels.