Disease is a significant issue to aquaculture, and bacterial infections are common, yet our understanding of how fish host microbiomes interact with the bacterial diversity in their environment is limited. The goal of the current study was to understand how external microbial diversity interacts with the internal microbiome of fish. To do this, we acclimated a euryhaline fish to a range of salinities, and measured the bacterial diversity in their aquaria water and microbiomes.