Urchin died

[monocus]

most likely old age.it got hollowed out by bristle worms and your clean up crew

[whatcaneyedo]

I've had a rock boring urchin for over three years but none of my tuxedos have lived more than 2. They can be killed quite easily too, in my experience a small fluctuation in salinity will certainly do it.

[Reef Pilot]

One of my other urchins is also a Tuxedo, but he was always more active, and loved to carry stuff around on his back. But this one never did, and did not move as much. So maybe he just wasn't as healthy to begin with, although he did last about 10 months or so.

When I feed my fish, no food makes to the bottom, so not sure if urchins need to be fed. I thought they just ate algae and coralline algae. Maybe he did starve.