My goldfish has been swimming like he's drunk for a week and has developed a lump under his skin on one side. It is the size of a marble now. Today, he is just lying on the bottom. He will get up and swim around to eat when I drop in food. My other two fish are just fine. (A month ago, another of my goldfish died after lying on the bottom - while still eating - for 2 weeks). That one had no other symptoms. What is this lump and how should I treat it? Thanks
