[header] How to make a goldfish live for decades [title] Get the largest possible tank. [step] Do not use a fish bowl; at least 75 liters (20 gallons) is necessary to make quality life for a single fish. Choose a tank with large surface area to increase the amount of oxygen in contact with the surface of the water (wider is better than taller). 
[title] Set up the tank prior to the purchase of a goldfish. [substeps] Getting it ready may take four or more weeks.