fancy what? You don't specify the species.... and that is needed in order for anyone to help.
whoops, just read again and the species is listed as a lionhead,.... sorry about that. Is your fish gulping at the surface? What kind of food are you feeding. If you are feeding flakes, you need to soak the flakes prior to putting them into the tank so that they sink. Goldfish, especially round bodied ones should not have floating foods as a part of their diet as it can lead to swim bladder issues and often does. When buying new food, be sure to select the sinking pellets.