Goldfish are one of the most common types of fish. They come in different varieties such as Ryukin, Fantail, Oranda and many others. Some goldfish look like they have bubbles of skin covering their eyes. Goldfish can live to be 5 to 10 years old. The average goldfish lives to be around 4 years old and can grow to be 6 inches plus. Goldfish originated in China with several hundred varieties developing over the years. They arrived in the United States somewhere between the 18th and 19th century and have became the most common pet found in households today! They have been kept as pets longer than any other species of fish. Although there are many varieties, all goldfish actually belong to just one species: Carassius auratus. Because of this, goldfish are similar in their behavior, required care, and habits. Goldfish are not tropical fish; therefore, they do not require tropical temperatures such as some fish with temperatures of 80F and higher.Goldfish are quite intelligent and will recognize the person who feeds them, research show that goldfish have a memory-span of at least three months and can distinguish between different shapes, colors and sounds. They will show they know you by swimming rapidly back and forth when you are near the tank or splashing. Goldfish like to play and benefit from the exercise, so having two fish is better than one. There are several varieties of goldfish; however, they all stem from the original stocks developed by Chinese, Korean, and Japanese breeders. Names are sometimes a hard thing to decide on due to the fact that different cultures call the same fish by different names. Goldfish come in many variations with different colors, single-tails, double-tails, various body shapes, head shapes from pointed to square, and various other mutations such as telescoped eyes.