Manic Fury
Aquarium Advice Activist
Gravel does not aid in digestion. This is one of those ridiculous myths that I am honestly not sure how it was even propagated. Goldfish (as well as other cyprinids) have pharyngeal teeth that allow them to 'chew' food in a sense. Trust me, trying to extract gravel from a goldfish with forceps is not fun!
Picture of pharyngeal teeth in goldfish:
File:Schlundknochen Goldfisch.JPG - Wikipedia, the free encyclopedia
Oh neat! Didn't know that. I knew it was a little ridiculous. Thanks for the anatomy lesson.