Given the paucity of information with regards the micronutrient requirements of the currently expanding number of cultured marine species, a series of investigations was undertaken to examine the water-soluble vitamin nutrition of the gilthead seabream (Sparus aurata L.). A preliminary study identified the qualitative requirement of this species for ascorbic acid, the B complex vitamins and choline for the maintenance of health and optimum productivity. Based on the observations of the preliminary experiment, a study was designed which allowed the development of a semi-purified diet and illustrated the qualitative requirement of the gilthead seabream for thiamin, niacin, riboflavin, pyridoxine and pantothenic acid. Using the semi-purified diet, the requirement for niacin and biotin were also established. As one of the vitamins for which the seabream exhibited a strong requirement, pyridoxine was chosen as the focus for an experiment which evaluated the benefit of the incorporation of this vitamin within a practical diet at levels which exceeded the minimum requirement. Thiamin is a vitamin which is known to exhibit a distinct relationship with carbohydrate metabolism, hence this vitamin was chosen as the focus of an investigation of the potential for the modification of vitamin requirements in response to major nutrient supply. Finally, having illustrated the requirement of gilthead seabream growers for ascorbic acid, an experiment was carried out to evaluate the efficacy of a series of vitamin C derivatives as feed supplements for this species. The current series of investigations has not only served to expand the present knowledge of the vitamin nutrition of the target species but has highlighted the potential for novel and applied research which remains within the field of micronutrients.