What kind of filtration and does it have a protein skimmer, as well? You don't mentiona a cleanup crew, either? How old is the tank?
Dependant upon these particulars, you're probably okay to add the goby. Goby's are carnivores and will require meaty foods, such as thawed shrimp (mysis) and optimumly, your tank is old enough that it will have critters (amphipods/copepods) living in the LR that it can snack between feedings.