My tuxedo urchin definitely ate a lot of coralline. I liked that, but your opinion might differ. Sometimes, people are lucky finding an animal to eat an alga, but more often than not, locating the right grazer is impractical. I might try some physical pruning (no more than a few minutes a week), some nutrient control, and perhaps a hydrogen peroxide or lime treatment if I got desperate. GFO sometimes helps, for example.