Petroleum, a fossil fuel, supplies more energy to the world today than any other source. The United States is the world's leading consumer of petroleum; in 1994, Americans used 7,587,000 barrels of oil per day.
Frequently test for ammonia and nitrite (you want both to measure zero). A pH test is also handy to ensure your goldfish's water is not too alkaline or acidic. This can be purchased at any pet store. Do not modify the fish's water, however, unless it is significantly different from neutral.
Of course, because goldfish live under water, they have a very different respiratory physiology than mammals have. For example, like most other aquatic fish, goldfish are adapted to breathe water instead of air, using a one-way-flow respiratory system.