A self-contained aquaculture system comprising a modular building defining a first main chamber for containing fish or marine invertebrates, a second swirl chamber comprising a primary filter communicating with the main chamber for removing solids from the main chamber, a drum filter for receiving and filtering water from the swirl chamber, a third biological filter chamber beneath the drum filter for receiving water therefrom and a biological filter tank. Water is pumped from the chamber. The building defines an enclosed space over the chambers, the temperature of which is controlled by an air conditioning unit. A foam fractionator, ultraviolet unit and ozone generator are used for treating the water in the main chamber.