[3][7] The main exhibit is a 1,000 m2 (11,000 sq ft), 5,000,000 L (1,300,000 US gal) tank with four large 49 m2 (530 sq ft) acrylic windows on its sides, and smaller focus windows strategically located around it to make sure it is a constant component throughout the exhibit space.

It is 7 m (23 ft) deep, which allows pelagic swimmers to swim above the bottom dwellers, and provides the illusion of the open ocean.

About 100 species from around the world are kept in this tank,[1] including sharks, rays, barracudas, groupers, and moray eels.

[8] Four tanks around the large central tank house four different habitats with their native flora and fauna: the North Atlantic rocky coast, the Antarctic coastal line, the Temperate Pacific kelp forests, and the Tropical Indian coral reefs.

[9] The Lisbon Oceanarium is one of the few aquariums in the world to house a sunfish[citation needed], because of their unique and demanding requirements for care.