Purple Monster Zoas straddle the line between Zoanathids and Palythoas, having the large heads of palys but growing directly against the rock like zoas.  Regardless of how they are classified, they make a beautiful addition to any reef tank.  They have large polyps with a purple centre surrounded by a bright, neon green skirt.  Like all zoas and palys they grow by budding and form a colony with all the polyps connected by fleshy tubes.  While they may take a while to start growing in a home aquarium, they are generally considered to be fairly fast growers once established.