Aquarium hobbyists know there are no fish who eat poop; although less-informed pet store associates might tell you otherwise. Poop is only expelled after extracting nutrients and energy from its food source and expulsion by excreting as waste product called feces which contains the same ammonia that the original release contained; over time this waste biodegrades to return this ammonia back into the water.
Coral-eating parrotfish feed on the algae found on coral reefs, but even this high-quality, low-cost source of nutrition does not provide all their required micronutrients. Therefore, these parrotfish supplement their diet with poop which contains abundant micronutrients and also includes the vital symbiotic dinoflagellate algae needed by coral to survive.
Hannah Rempel, a Ph.D. student at the University of Texas Marine Science Institute and co-author of a recent study co-authored by Hannah Rempel demonstrates that coral-eating fishes--known as corallivores--are filled with beneficial microbes that maintain coral health. This discovery disproves long-held beliefs that these fish were harming reef structures by eating detritus and bushy algae; rather, this opens doors for using transplanted fecal material to revive stressed-out corals affected by coral bleaching phenomena. Read the article published at Nature Communications here.
