An aquaculture system (1) for farming aquatic organisms includes an apparatus (2) for supplying oxygenated water into an enclosure (20) in which aquatic organisms are to be fanned. The apparatus (2) includes a water inlet (4) and an oxygen inlet (6) to create a water and oxygen mixture. The apparatus (2) also includes a venturi (17) arranged to dissolve the oxygen into the water passing through the venturi and such that the oxygen and water mixture passing through the venturi (17) is exposed to a substantially null magnetic field. The apparatus is also arranged such that the water and oxygen mixture that is supplied to the venturi (17) contains substantially no colloidal minerals. The apparatus also includes an outlet (18) for the oxygenated water in fluid communication with, and downstream of, the venturi (17) and in fluid communication with the inlet of the enclosure (20).
