I purchased what i believe to be a variegated urchin and a white urchin. I was told that they would put a hurting on my hair algae. They like basically everything else in my tank will not touch it. They are destroying my coraline algae though. Which I think may be counter productive because it looks like the gha struggles to grow with the coraline is and they are removing TONS of coraline. Has anyone else experienced this?