Most urchins are voracious algae grazers, but some species have an appetite for meat. Watch this time lapse video of an opportunistic urchin consuming a dead chromis. Public service announcement: Even herbivorous urchins can turn carnivorous when starved of algae, so make sure to feed your urchins if your tank is free of algae (lucky you!).
I'm a passionate aquarist of over 30 years, a coral reef lover, and the blog editor for Advanced Aquarist. While aquarium gadgets interest me, it's really livestock (especially fish), artistry of aquariums, and "method behind the madness" processes that captivate my attention.