After snorkeling a little ways down the reef I started seeing more and more large Sleek Unicornfish. Until finally I came to a spot where hundreds were gathered together in a rare spawning event. This is where the plankton was coming from that was feeding the mackerel scad. Male unicornfish were displaying beautiful courting colors and patterns as they chased females around trying to impress them.
I took a video of the unicornfish in action and you can see the change in coloration and patterns on the courting males. I was amazed to see them change from all dark to yellow fins, blue markings on the face, and an iridescent bar over their eyes.
You can see the video here: http://www.youtube.com/watch?v=SbMIaJWtwW8