Is a polyp a herbivore?
No a herbivore would be something like a giraffe, a polyp is a tumerous growth.
A coral polyp grows when the new planula* lands on a nearby coral. Then, as time passes the planula* turns into a coral polyp. The coral that the polyp is on feeds the polyp and the polyp starts to grow. When the polyp is grown enough it can then spawn (which means to have sexual activity). As time passes the polyp becomes a grown coral.