Long Spine Urchin eating coral?

Has anyone seen a Long Spine urchin eating coral such as Clove Polyps? I had a few Clove Polyps not doing so well. My urchin was lurking nearby. The next morning the Clove Polyps are totally gone. This has happened twice now. I have not fed him sea weed because there is adequate algae on the rock I want him to eat. I put some sea weed in last night but it was still there in the morning. During the day the sea weed disappeared along with a couple more Clove Polyps. And I am running low on Clove Polyps.