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.
Goldfish need appropriate temperatures to remain healthy. Goldfish are cold water fish who live in cool lakes, streams and rivers. However, the fact that they are cold water fish does not mean that they should be kept in frigid temperatures.