Why do parrotfish make sand?

Answer: Pooping out coral skeletons

Pooping out coral skeletons ✓ — Correct! Parrotfish have beak-like teeth that scrape algae off coral reefs. They eat the coral skeleton along with the algae. Their digestive system extracts nutrients and grinds up the calcium carbonate, then excretes it as fine white sand. One large parrotfish produces 200+ pounds of sand yearly—creating beaches!

Grinding rocks for minerals — Wrong. Parrotfish target coral specifically for the algae growing on it, not rocks for minerals. The sand is a byproduct of feeding, not intentional.

Filtering sand from water — Wrong. Parrotfish create sand, not filter it. They bite coral, digest the algae, and excrete pulverized coral skeleton as sand.