I did something today that I rarely ever do, I made an impulse purchase. I saw a fish in my LFS that caught my attention. I asked the employees what type of fish it was and none of them had any idea what it was despite them having it for a week. One of them took a picture of it and sent it to a manager and he/she told them that it was a jack dempsey. I clearly knew that this fish had no relation to a dempsey. The decided the price would be $24.99 so I bought it. I felt that it was some sort of goby and looked up freshwater gobies and looked for large ones. I came upon a species called sleeper gobies. When I looked further into them I learned that mine goes by the common names "Jade/Jade sleeper goby or Fat sleeper goby. From the info I have read these gobies get pretty big. What I am confused about is if it is freshwater or brackish water? I also wanted to know if it is compatible with my current stock: Oscars, Senegal Bichir/Polypterus, Lima Shovelnose Catfish, and ID Sharks. He seems to be fitting in well so far, but I wanted to make sure there will be no issues down the road. I hope that he will work out because it is a striking fish and is already very active in my tank despite only being in there for a couple of hours. Is there any need to know care information?