Corals are colonized by symbiotic microorganisms that exert a profound influence on the animal’s health. One noted symbiont is a single-celled alga which provides the coral with most of its carbon. During thermal stress, the algae’s photosystems are impaired, resulting in a toxic accumulation of reactive oxygen species (ROS) that cause cellular damage to both the host and symbiont. As a protective mechanism the algal symbionts are lost this process is known as bleaching. Our goal is to construct a probiotic comprised of host-associated bacteria able to neutralize free radicals such as ROS. Our experimental system is the coral model, the anemone Exaiptasia diaphana, and pure bacterial cultures isolated from the model animal. Using a 2,2-diphenyl-1-picrylhydrazyl (DPPH stable free radical) assay, we have identified six strains with high free radical scavenging ability belonging to the families Alteromonadaceae, Rhodobacteraceae, Flavobacteriaceae, and Micrococcaceae. In parallel, we have established a “negative” probiotic consisting of closely related strains with poor free radical scavenging capacity. From their whole genome sequences, we aim to describe the genetic basis for this variability between closely related strains this information can help facilitate the therapeutic application of a bacterial probiotic. Probiotics is one of several human interventions currently being developed with the aim of augmenting climate resilience in corals and increasing the likelihood of coral reef persistence into the future.