A public aquarium (plural: public aquaria or public aquariums) is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquaria feature tanks larger than those which could be kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-1800s, they have become popular and their numbers have increased. Most modern accredited aquaria stress conservation issues and educating the public.
The first public aquarium was opened in London Zoo in May 1853; the "Fish House", as it came to be known, was constructed much like a greenhouse. P.T. Barnum quickly followed in 1856 with the first American aquarium as part of his established Barnum's American Museum, which was located on Broadway in New York before it burned down. In 1859, the Aquarial Gardens were founded in Boston. A number of aquaria then opened in Europe, such as the Jardin d'Acclimatation in Paris and the Viennese Aquarium Salon (both founded 1860), the Marine Aquarium Temple as part of the Zoological Garden in Hamburg (1864), as well as aquariums in Berlin (1869) and Brighton (1872). The oldest American aquarium is the National Aquarium in Washington, D.C., founded in 1873. This was followed by the opening of other public aquaria : San Francisco (Woodward's Garden, 1873-1890), Wood Hole (Science Aquarium, 1885), New York (Battery Park, 1896-1941), La Jolla (Scripps, 1903), Detroit (Belle Isle, 1904-2005), Philadelphia (Fairmount Water Works, 1911-1962), San Francisco (Steinhart Aquarium, 1923), Chicago (Shedd Aquarium, 1929). For many years, the Shedd Aquarium in Chicago was the largest aquarium in the world, until the Georgia Aquarium in Atlanta opened.
In 2005, the Georgia Aquarium, with more than 8 million US gallons (30,000 m³; 30,000,000 liters) of marine and fresh water, and more than 100,000 animals of 500 different species opened in Atlanta, Georgia. The aquarium's notable specimens include whale sharks and beluga whales.
Modern day aquarium tanks can hold millions of U.S. gallons of water and can house large species, including dolphins, sharks or beluga whales. This is accomplished though thick, clear acrylic glass windows. Aquatic and semiaquatic mammals, including otters, and seals are often cared for at aquaria. Some establishments, such as the Oregon Coast Aquarium, have aquatic aviaries.
Most aquaria will have special exhibits to entice repeat visitors, in addition to its permanent collection. A few have their own version of a "petting zoo"; for instance, the Monterey Bay Aquarium has a shallow tank filled with common types of rays, and one can reach in to feel their smooth skins as they pass by.
Also as with zoos, aquaria usually have specialized research staff who study the habits and biology of their specimens.
Most public aquaria are located close to the ocean, for a steady supply of natural seawater. An inland pioneer was Chicago's Shedd Aquarium that received seawater shipped by rail in special tank cars. The early (1911) Philadelphia Aquarium, built in the city's disused water works, had to switch to treated city water when the nearby river became too contaminated. Similarly, the recently opened Georgia Aquarium filled its tanks with fresh water from the city water system and salinated its salt water exhibits using the same commercial salt and mineral additives available to home aquarists.
In January 1985, Kelly Tarlton began construction of the first aquarium, Kelly Tarlton's Underwater World, to include a large transparent acrylic tunnel in Auckland, New Zealand, a task that took 10 months and cost NZ$3 million. The 110-meter tunnel was built from one-tonne slabs of German sheet plastic that were shaped locally in an oven. A moving walkway now transports visitors through, and groups of school children occasionally hold sleepovers there beneath the swimming sharks and rays.