* Algae: They graze on a variety of algae, including seaweed, kelp, and phytoplankton.
* Diatoms: These microscopic algae are a significant part of their diet.
* Detritus: They also feed on decaying organic matter found on the ocean floor.
They use their sharp teeth to scrape algae off rocks and other surfaces. Some species even have special structures called "Aristotle's lantern" that help them grind and break down their food.