An aquarium is a water-filled tank, usually with glass sides, in which aquatic plants and animals, particularly fish, are kept. The term is applied to single tanks for home use in which fish are kept for their decorative effect and interesting habits and to public institutions with tanks for exhibition and scientific study of aquatic life.
Home aquariums are often made to simulate a natural environment. Aquatic plants supply the oxygen needed by the fish, but often an aerating device is used to furnish additional oxygen. Goldfish enjoy cool water, but the popular tropical fish must have water at a constant temperature of 22 degrees C (72 degrees F) or more.
Aquarium keeping is a popular hobby around the world, with about 60 million enthusiasts worldwide. A wide variety of aquaria are now kept by hobbyists, ranging from a simple bowl housing a single fish to complex simulated ecosystems with carefully engineered support systems.
The careful aquarist dedicates considerable effort to maintaining a tank ecology that mimics its inhabitants’ natural habitat. Controlling water quality includes managing the inflow and outflow of nutrients, most notably the management of waste produced by tank inhabitants. The nitrogen cycle describes the flow of nitrogen from input via food, through toxic nitrogenous waste produced by tank inhabitants, to metabolism to less toxic compounds by beneficial bacteria populations. Other components in maintaining a suitable aquarium environment include appropriate species selection, management of biological loading, and good physical design.
The first scientific and popular aquarium was erected in the London Zoological Gardens in 1853; it was closed shortly afterward, and a new one was not erected until 1924. Other large European aquariums were built in Plymouth, England; Paris and Nice, France; Naples; and Berlin; all but the last survived World War II. Marineland, near Saint Augustine, Florida, represented a new trend in public aquarium architecture when it opened in 1938. Since then, most new aquariums, often called oceanariums or seaquariums, have been located on the ocean or on a bay or river and feature outdoor pools and aquatic environments with clear acrylic windows and portholes that enable visitors to see large and small fish and other marine life from below the water surface.
Among the famous public aquariums in the United States are the Steinhart Aquarium in San Francisco, the Shedd Aquarium in Chicago, the New England Aquarium in Boston, and the Aquarium for Wildlife Conservation in Coney Island, Brooklyn, New York, at which the Osborne Laboratories of Marine Sciences are located.