Swimming fish | Aquarium fish feed | Ocean Park

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 City before it burned down. In 1859, the Aquarial Gardens were founded in Boston. A number of aquariums 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 old Berlin Aquarium opened in 1869. The building site was to be Unter den Linden (along a major avenue), in the centre of town, not at the Berlin Zoo. The aquarium's first director, Alfred Brehm, former director of the Hamburg Zoo from 1863 to 1866, served until 1874. With its emphasis on education, the public aquarium was designed like a grotto, part of it made of natural rock. The Geologische Grotte depicted "the strata of the earth's crust". The grotto also featured birds and pools for seals. The Aquarium Unter den Linden was a three-story building. Machinery and water tanks were on the ground floor, aquarium basins for the fish on the first floor. Because of Brehm's special interest in birds, a huge aviary, with cages for mammals placed around it, was located on the second floor. The facility closed in 1910.

The Artis aquarium at Amsterdam Zoo was constructed inside a Victorian building in 1882, and was renovated in 1997. At the end of the 19th century the Artis aquarium was considered state-of-the-art, as it was again at the end of the 20th century.

Prior to its closing on 30 September 2013, the oldest American aquarium was the National Aquarium in Washington, D.C., founded in 1873. This was followed by the opening of other public aquariums: San Francisco (Woodward's Gardens, 1873–1890), Woods Hole (Woods Hole Science Aquarium, 1885), New York (New York Aquarium, 1896–present), La Jolla (Scripps, 1903), Honolulu (Waikiki Aquarium, 1904–present), Detroit (Belle Isle Aquarium, 1904–2005, 2012–Present), Philadelphia (Philadelphia Aquarium, 1911–1962), San Francisco (Steinhart Aquarium, 1923), Chicago (Shedd Aquarium, 1929). For many years, the Shedd Aquarium was the largest aquarium in the United States until the Georgia Aquarium in Atlanta opened 2005. Entertainment and aquatic circus exhibits were combined as themes in Philadelphia's Aquarama Aquarium Theater of the Sea (1962–1969) and Camden's re-invented Adventure Aquarium 2005, formerly the New Jersey State Aquarium (1992).

The first Japanese public aquarium, a small freshwater aquarium called "Uonozoki", was opened at the Ueno Zoo in 1882.

Modern aquarium tanks can hold millions of litres of water and can house large species, including dolphins, sharks or beluga whales. This is accomplished through thick, clear acrylic glass windows. Aquatic and semiaquatic mammals, including otters and seals are often cared for at aquariums. Some establishments, such as the Oregon Coast Aquarium or the Monterey Bay Aquarium, have aquatic aviaries. Modern aquariums also include land animals and plants that spend time in or near the water.

For marketing purposes, many aquariums promote special exhibits, in addition to their permanent collections. Some have aquatic versions of a petting zoo. The Monterey Bay Aquarium has a shallow tank filled with common types of rays which visitors are encouraged to touch. The South Carolina Aquarium lets visitors feed the rays in their Saltmarsh Aviary exhibit.

The largest public aquarium is the Chimelong Ocean Kingdom theme park, opened in 2014 in Hengqin, Zhuhai, with a total of 48.75 million litres (12.87 million US gal) of water. The second largest is the Marine Life Park in southern Singapore with a total of 45 million litres (12 million US gal) of water for more than 100,000 marine animals of over 800 species.

Ocean Park Hong Kong, commonly known as Ocean Park, is a marine mammal park, oceanarium, animal theme park and amusement park situated in Wong Chuk Hang and Nam Long Shan in the Southern District of Hong Kong. It is the second largest theme park in Hong Kong, after Hong Kong Disneyland, as well as the largest theme park in Hong Kong by area. It is also the second oldest theme park in Hong Kong, after the now-defunct Lai Chi Kok Amusement Park which closed on 31 March 1997, four months before the 1997 handover.

Opened on 10 January 1977, Ocean Park became popular, but 28 years later, it was unprofitable and widely expected to close due to the new Hong Kong Disneyland. However, the Park responded with a HK$5.5 billion development plan that saw it expand to over 80 attractions and rides, and steadily grow visitor numbers to 7.6 million in 2014, making it the world's 13th most visited theme park, and one of the largest theme parks in Asia.