Urchin expelling black stuff

[carpetlover]

My tux seems happy as he is carrying macro algae on his back, but he is excreting black poop like things everywhere he goes. I heard that their poop is sand like, so I have no idea what it is. Can anyone help?
Pics: my urchin, then his black excrement

 

[Ron Reefman]

IMHO, if it seems to be doing OK, I wouldn't worry too much. Besides, what would you do if it was a sign of being in poor health?