This present utility model discloses the methods of fattening oysters using plankton as food in the semi-close recirculating system. Fattening of oysters comprising the steps of； cleaning and rinsing of oyster culture water tanks, providing 3-4 layers' trays to hold oysters during the entire 30 days fattening period, stocking 6.0 - 12 cm size oyster not exceeding 50 pcnt tank water capacity, providing mild aeration using portable aerators to keep plankton in suspension, removing of dirt and suspended particles through siphoning before water intake, continuously allowing water from a plankton pond to flow into the oyster culture tank for 30 days to ensure that green colour of water is maintained, and for depurating oysters, allowing water by flow through for 24 hours a day before harvesting using clean seawater to clean oysters by purging our dirt and contaminants from their digestive tract.
