Read up before you buy any fish! CYCLE your tank before adding the fish. Do weekly water changes. 10 gallons per goldfish is ideal, more is better. Dont trust pet store employees.
I like my coffee black just like my metal.
I love fancy goldfish. People dont give them enough credit. They are gorgeous fish and very rewarding. They are not throw aways and need large tanks with good filtration.
When you see signs of stress in your fish, you can then take steps to identify the source of that stress and then to resolve it before it becomes a major issue.
If you're looking for a unique way to stock your new tank, give freshwater shrimp a try.
If your fish is suffering, you may want to consider euthanasia as an option to humanely end his pain.