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.
So one simple way to have a goldfish living in perfect water is to have two bowls. Each day the fish can be moved to the other bowl, while the first bowl can be emptied, wiped clean and refilled with water that will be ready for the fish to live in the next day.