Can some one help I’d this fish

[Fishology]

I asked my grandfather if you can bring me a goby for Chicago form a local fish store, when he arrived he said he had gotten another fish for the tank, I can’t find a fish that matches, can some one help Id pls?

 

[Tuan’s Reef]

Its a Mono.... brackish fish

ad from liveaquaria

 

[Sharkbait19]

Definitely a mono.
They can survive from fresh to salt, but generally brackish is best (as with all fish like that).