Urchin ID?

[reefwars]

ive kept a rock boring urchin in my overflow for about going on 3 yrs now lol he lives in a 8 x 6 x 12 box , there's nothing in there but coraline for him to eat and i dont feed the urchin anything and often forget hes in there for months on end just to keep finding him alive and bigger than before lol i use to pick him out of there but he kept insisting on going back so stay there he did