Parrotfish
Depth: 20 m · Sunlight Zone
The parrotfish has a beak like a parrot and uses it to nibble algae off the coral. In doing so it also grinds up limestone, which it releases again as fine white sand. Many beaches are partly made of this fish sand. At night it sleeps inside a bubble of slime it makes itself.
For scientists
The fused teeth of the parrotfish form a hard beak; further tooth plates in its throat grind the coral limestone, so a single fish can produce hundreds of kilograms of sand a year. At night it wraps itself in a mucus cocoon that hides its smell and keeps parasites away. Many species change sex and color during life, from drab to brilliantly colored.
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