The use of outdoor ponds has been the prevalent method for hatchery production in South East Asia. In Singapore, due to constraints in land availability and seawater accessibility, farms are transforming towards the use of Recirculating Aquaculture System (RAS) for hatchery production. RAS overcomes the constraints of outdoor pond culture and indoor flow-through system as it requires a small foot-print, reduces seawater usage and allows better control of water parameters. The closed recirculating aquaculture system also helps to minimise the risk of disease with proper treatment of incoming water. With the application of RAS Technology in hatchery production, we have developed the hatchery protocols for a low-salinity RAS to manage Big-belly disease syndrome (BB), a highly pathogenic bacterial disease that affects Asian Seabass causing mortality to reach up to 70% within a week. By lowering the salinity in a RAS, we could prevent BB disease outbreak as the culture condition becomes unfavourable for the halophilic bacteria. This topic describes the hatchery protocol developed for Asian Seabass in low-salinity RAS and include some examples of RAS application in commercial hatcheries.