Why can oceanariums display more fish species than freshwater aquariums?

Oceanariums are able to display a greater diversity of fish species compared to freshwater aquariums primarily because there is a significantly higher number of different fish species that inhabit marine environments than those found in freshwater systems.1

Beyond this biological diversity, oceanariums utilize very large tanks—sometimes holding up to 1,000,000 gallons—which allow for the display of large and impressive marine animals, such as sharks, rays, and sea turtles, alongside seagoing mammals like whales and dolphins. While maintaining these saltwater environments is more complex due to the challenges of managing salinity, temperature, and acidity, the scale and nature of these facilities enable a broader range of species to be housed together in community-style exhibits.12