I need help sorting my tank out! :(

[my2rotties]

My green brittle star ate my scooter blenny. I saw him reach out and grab the fish and there was nothing I could do. I just got rid of all my large red hermit crabs, since I found one of them eating the legs off of my sandsifting starfish. I have two black spined sea urchins and want them out... just don't know how to go about doing it at this point. Like Aquattro said they knock everything over. They also grow super big in no time at all.

I have been trying to remove the brittle star but he is under a rock at the bottom of my tank.

I also had a tomato clown with my maroon clown. Had to rehome the tomato since the maroon was trying to beat him to death.