Are sea urchin omnivores?
Yes, they are.
I think a sea anenome and a sea urchin can live together because i have a little aquarium and there is a sea urchin and and a sea anenome (if that's how you spell it) living in there and they were perfectly fine. BUT if you have a sea urchin do not have any crabs in there, because my sea urchin killed one, and almost killed another one by taking its claw off. :(
There are over 700 species of Sea urchins. Some examples would be the pincushion sea urchin, the popular and common longspine urchin, the Blue Tuxedo urchin, the shortspine urchin and the pencil urchin. They usually differ in color, location most common and overall look or how long their spines are.