Photo/Illutration

Editor's note: This is part of a series of videos offering an up-close perspective on the animal kingdom. A special 360-degree video camera system was set up in zoos and other facilities to show how the animals view their world as they interact.

Also visit our special 360-DEGREE LIVES page (http://t.asahi.com/360lives), where you can watch all the previous videos.

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The goldfish is an iconic image of summer in this country, beloved by Japanese since the Edo Period (1603-1867).

The sight of a few swimming leisurely but gracefully in fish bowls is said to make one feel cool on a hot summer day.

Seeing about 500 of them in a 30-ton tank takes cool to a whole other level.

The 2.3-meter-high, 5.5-meter-wide tank at The Adachi Park of Living Things in Tokyo’s Adachi Ward is one of the largest tanks for keeping and displaying the fish in the country.

About 35 varieties of the omnivorous fish are on show, including the twin-tailed “wakin,” “demekin” (telescope eye) and the hooded “ranchu.” The lionhead, which originated in China and has a hump similar to the king of the jungle’s mane, and the “tancho,” characterized by its red hump and white body like a red-crowned crane, are particularly mesmerizing to watch.

“It’s rare to see a wide variety of goldfish swimming in groups,” said Tomoo Unagami, 30, a head keeper at the park.

Having active goldfish and poor swimmers in the same tank can be problematic. Park officials said they made it possible by adjusting water currents and providing hiding spots for the fish.

According to Unagami, goldfish originated from a breed of crucian carp more than 1,700 years ago in China. Selective breeding there and in Japan later produced diverse varieties of the species.

The wakin, which kids often try to catch at summer festival concessions, can grow to 30 centimeters or more in length. Goldfish are believed to live for at least 10 years. The oldest one recognized by Guinness Book of World Records died at the age of 43.