The Red Metallic Urchin has a rusty red coloration with blue metallic dots. This beautiful can be found grazing algae on the reef. The Red Metallic Urchin is known for its herbivore diet. Diadema urchins do not prey on fish or invertebrates and are generally coral safe, but they may graze polyps while in search of algae. This long spined urchins' spines are mildly poisonous and may cause a slight skin reaction in humans if they are stuck by them. Handle with care.