I presume you are talking about the Marbled sleaper goby Oxyeleotris marmaoratus? This is one of the largest goby species and one of the most predatory, the fish lies in wait for its prey to pass over head and then attacks from below swallowing its victim whole. It can reach lengths of around 20" so if you dare to have any tankmates they should be at least 15" to avoid being seen as food. The fish preffers a slightly brackish enviroment and is nocturnal so will need large caves and/or bogwood in which to shelter under by day, a sand substrate would be preffered so the fish can burrow.