Larval white seabass (Atractoscion nobilis) culture at the Hubbs-SeaWorld Research Institute utilizes Artemia as a live feed, but is sometimes hindered by pathogenic bacterial overgrowth in the live feed production process. A commercially available probiotic, Sanolife® MIC (INVE Aquaculture), was tested for its ability to modify microbial populations in both live feeds and white seabass culture tanks. Sanolife® MIC was administered to either Artemia storage tanks or directly to larval rearing tanks. Outcomes of microbial diversity, microbial composition, larval growth and performance were compared across four distinct treatment groups: Artemia with Sanolife® MIC, larval culture water with Sanolife® MIC, non-probiotic control, and addition of Rotifers to standard feeding protocol. Growth and survival of fish in each treatment was monitored weekly. Samples for microbiome analysis were collected from Artemia storage tanks, larval fish culture water and larval white seabass at various time points during the first two months of life. Culturing on TCBS (Thiosulfate–citrate–bile salts–sucrose) media was also conducted in conjunction with microbiome sampling to evaluate growth of potentially harmful bacteria over time across the different treatments. To achieve a broader understanding of total bacterial community characteristics across treatments, Artemia, larval fish and larval culture water were sequenced using 16S rRNA amplicon sequencing. The primary goal of this study is to assess correlation between microbiome characteristics and white seabass larval performance in aquaculture. Secondarily, this study assesses the relative contribution of live feeds and culture environment to the larval white seabass microbiome over time. Probiotics are a promising solution to increase the success of larval fish rearing, but fundamental knowledge on the interaction between probiotics and the microbiome is still being developed.