Sea urchin??

that thing is epic man

 

i would say not even a inch across in diameter but he has grown since i first saw him. he occasionally gets muck all over him so i have to clean him... other then that i like him

 

That muckh has probably been placed on there by the urchin. They take bits of their environment and stick it to their bodies to blend in and avoid predation. Mine took a notion to stick a maxima clam and coral frags to its back. I got rid of the urchin because I was afraid that the urchin would drop those animals somewhere behind the rockwork where they would surely die.