I had the niger, the giraffe, and the vulture. I would not do any of them if you want to keep them long term. They all are food aggressive and will take most of the food from the slower fishes. The vulture will be aggressive toward the other fishes. Mines attacked my fly river turtle and caused some major damage. A 180 gallon tank is fairly small when you are talking about those cats. You should stick with the larger synodontis and smaller pictus cats. They will look proportional to the tank. Otherwise you will have a real monster in your tank. Good Luck.