Hasleaostrearia is a marine diatom that can feed oysters. This study aimed to cultivate H.ostrearia in the following media: seawater (SW), seawater filtered by activated carbon (SW+CA), and drilling water (DW). The three-water media were supplemented with two types of nutrients, Walne-Conway+silica (CS) and ES-1/3 Provasoli (P), leading to a six experiment series. The cultures were grown in 200 mL and 400 mL respectively. The dilution cycle was every 3 - 4 day for 200 mL volume and every 4 - 5 days for the 400 mL volume for 20 - 40 days or until the cultures showed a decrease in growth. The microalgae exhibited a better growth in SW and SW+CA CS, whereas DW showed a diminishing number of cells in both the CS and P medium. The highest value of Emn in the 200 mL volume presented in the SW CS medium (1.94 mg L−1) and in the SW+CA CS medium (8.16 mg L−1), while the lowest value of Emn was found in the SW+CA CS medium (0.42 mg L−1). Imn was apparent in the SW P medium (0.56 mg L−1). In conclusion, both SW CS and SW+CA CS showed a better performance in growth. The seawater was more stable during the experiment in both the 200 mL and 400 mL volumes.