Parrotfishes are abundant herbivores that primarily graze upon algae, which may indirectly benefit corals by mitigating coral-algae competition. At a local scale, management efforts to increase populations of parrotfishes are believed to be critically important to maintaining resilient, coral-dominated reefs. Yet, some parrotfish species also occasionally graze coral—a behavior known as corallivory. Corallivory can cause the partial to total mortality of coral colonies and may have long-term impacts such as reduced coral growth and reproductive capacity and increased susceptibility to disease. While evidence suggests that parrotfishes likely have an overall net positive impact on coral communities, they may have detrimental impacts on heavily predated coral species, such as O. annularis.
source https://phys.org/news/2020-12-recovery-endangered-caribbean-coral-parrotfish.html
