The fish used to be scratch ayapak eat coral and have another tooth in the throat. Which when abrasives to gnaw it as sound. Time taken to take a powder, sludge, which is beneficial to the coral reefs.
The fish eat the beaks scrape the coral. And another set of teeth in the throat. When it was a sound bite. Take time to take out the powder sediments, which are beneficial to the reef.
The fish use beaks scraped eat corals. And there is another set of teeth in the throat. When the nibble it is sound. The time taken to piss off powder of sediment, which is beneficial to the coral reef.