Cnidarians owe their success to endosymbionts of Family Symbiodiniaceae by providing hosts  energy via photosynthetic products. The phenomenon of bleaching is defined by the loss of these microalgae. Former collections of symbiotic cnidarians from the Indo-Pacific were reassessed with a modern multi-marker approach. Phylogenetic analysis identified multiple, independent groups of coevolution between host and symbionts, providing a better understanding of the evolution of this symbiosis, and revealing underlying host-symbiont association patterns critical to reef conservation.