Some large parrotfish species can poop up to 405 kg of sand each year. Although estimates vary, it’s clear that they can produce a lot of sand. Perry et. al (2015) found that up to 85 % of new sand on a beach in the Maldives was made by parrotfish.

In an effort to figure out why parrotfish teeth among the hardest in the world, Gilbert, Marcus, and Miserez used X-rays to map the teeth structures.

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Morgan and Kench (2016) “Parrotfish erosion underpins reef growth, sand talus development and island building in the Maldives” https://doi.org/10.1016/j.sedgeo.2016.05.011 

Perry, Kench, O’Leary, Morgan and Januchowski-Hartley (2015) “Linking reef ecology to island building: Parrotfish  identified as major producers of island-building sediment in the  Maldives” doi: https://doi.org/10.1130/G36623.1

Glenn Roberts Jr “X-Rays Reveal the Biting Truth About Parrotfish Teeth” https://newscenter.lbl.gov/2017/11/15/xrays-reveal-biting-truth-about-parrotfish-teeth/ published 15. november 2017, last accessed 6. february 2021