Some popular aquariums

For thousands of years, people have wanted to explore the world under the sea. Such activity was not possible until modern times. Today, divers can survive for hours underwater and photograph fish and other sea creatures.

Not everyone can swim with fish in the ocean. But they can enjoy underwater life in another way — by visiting an aquarium.Experts do not really know when people began keeping fish as pets. But they say that people have been interested in fish for thousands of years. Some say the ancient Sumerians were the first civilization to keep fish in ponds more than 4,000 years ago. The Chinese kept and studied carp and goldfish more than 1,000 years ago. The ancient Romans kept eels as pets. And the Greek philosopher Aristotle made what is believed to be the first known study of sea life, including sharks and dolphins.

Experts say that keeping fish at home in small water tanks called aquariums is extremely popular today. And everyone seems to enjoy visiting huge public aquariums that have opened around the world.

By the middle of the 1800s, science had shown that plants, fish and other sea creatures could survive together under water. So it was no longer necessary to change the water in a tank for fish to live there. This led to the building of the first public aquariums.

The first one opened in London, England in 1853. In the next 15 years, other aquariums opened in Europe and the United States. By 1928, there were about 45 public aquariums.

Today, millions of people visit aquariums in more than 30 countries. Steve Feldman is an official with the Association of Zoos and Aquariums in Silver Spring, Maryland. He says his organization has recognized and approved 41 aquariums in the United States. About 58 million people visit these places each year.

One of the most famous aquariums is in Monterey, California. Officials say the Monterey Bay Aquarium has been recognized as the finest aquarium in the United States. It is in a building that used to be a kind of factory called a cannery. This was where workers prepared fish and placed them in cans to be sold.

The Monterey Bay Aquarium shows visitors the underwater life in the bay. Scientists at the aquarium also study the animals and work to help many survive.

For example, the Monterey Bay Aquarium cared for 19 penguins from New Orleans, Louisiana. They were rescued after hurricane Katrina struck the area in 2005. These penguins were kept until they were ready to be returned to the Audubon Aquarium of the Americas.

The Monterey Bay Aquarium also works to save the sea otter. Aquarium workers rescue lost or hurt young sea otters and prepare them to survive in the wild. The ones that cannot be released are kept in the aquarium and entertain visitors by swimming quickly and playing tricks in the water.

Visitors especially enjoy watching them play with objects in the water. When sea otters find new objects, they smell them, hold them, play with them and hit them against other hard objects. The otters hit their toys against the walls of the tank in front of the happy visitors.

At the center of the Monterey Bay Aquarium is a huge tank more than eight meters high. It is one of the tallest aquarium exhibits in the world.

The tank holds more than one million liters of seawater and many different kinds of fish. It also holds more than 100 kinds of plants. Officials say the tank was built in the center of the aquarium because it would get the most sunlight each day. All this sun helps the plants grow — about ten centimeters every day.