The microbial communities of larval sablefish (Anoplopoma fimbria) reared in traditional "greenwater" vs. those reared in "claywater," an emerging alternative to greenwater, were assessed. Larvae were spawned and reared at the Manchester Research Station in Port Orchard, WA (NOAA Northwest Fisheries Science Center). Rearing tank seawater was sourced from Puget Sound. 16S rRNA gene sequencing (V3-V4 region) was carried out on larval skin swabs, whole larvae, rearing tank seawater, and tank surface swabs. Additional samples include the rotifer feed, algal paste additive (greenwater), clay additive (claywater), inflowing seawater, and sablefish hatching silos. The aim of this project was to understand the microbial community dynamics associated with each aquaculture water additive and their relationship to sablefish growth and survival.