The Aquarium provides a small-scale display of underwater wildlife in the area between the Museum and the Atlantic coast of the Cíes Islands, including three differentiated ecosystems: the coast, the estuary and the islands.
The influence of human action on the coast, with the building of docks and moles, has transformed the substrate and the water column. In this modified habitat a number of marine species —including sardine, white sea bream, gilthead, ballan wrasse, bream, conger eel, lobster and other shellfish and crustaceans— have found their shelter.
Alterations in the estuary are the consequence of the exploitation of mussel rafts: they transform the sandy bottom of the sea, which lose oxygen and become muddy.
The Cíes Islands enjoy a truly pristine and virginal ecosystem. This area of shaken waters is home to barnacles living on the rocks as well as to calcareous seaweed, which make up the Maërl bottoms. And this, in turn, is the habitat where pelagic fish such as saddled sea bream, black bream, bogue and sardine, and demersal fish such as pollock thrive.