Phytoplankton is the sole diet for larval oysters in hatchery systems, so enhancing their nutritional quality is very important to larval growth and survival. Although species selection in hatcheries emphasize lipid content, fatty acid profiles, and growth rates, less attention has been given to how stable and consistent these qualities remain throughout and between culture periods. In this research, I evaluated the variability in phytoplankton quality across 113 samples of Chaetoceros calcitrans, Tetraselmis chui, and Pavlova pinguis cultures used in the Virginia Institute of Marine Science (VIMS) Acuff Center hatchery from February to August 2024. Samples were collected at the start and harvest points of each culture cycle to measure pH, salinity, nutrient concentrations, cell abundance, chlorophyll-a, ash-free dry weight (AFDW), C:N:P ratios, and fatty acid composition. The preliminary findings suggest that water quality parameters such as pH, dissolved oxygen varied across some cultures, despite efforts to control them through CO₂ regulation, temperature stabilization, sterilization of source water, and standardized media enrichment. This variability may influence the quality of phytoplankton when they are harvested, potentially affecting the nutritional consistency of prey available to oyster larvae. This study highlights the importance of monitoring and optimizing culture conditions not only for biomass production, but also for maintaining stable nutritional profiles throughout hatchery operations. Understanding and minimizing these fluctuations is essential for ensuring reliable larval diets and improving hatchery performance.