Common Urchin

A hitchhiker from some Live Rock I purchased is cleaning the glass. They're not particularly a fan of light, and tend to run away from light when it's shined on them, allowing them to be "moved" without touching them.

In this case, it was cleaning the front glass of my tank, which I had neglected to scrape for a bit. This tends to please my Turbo Snails as well, who then jump on the glass.

This picture was taken near midnight.