It’s beginning to look a lot like coral spawning.
The Florida Keys site has a nice write up of the coral spawning event that will likely take place during the full moon in either August or September.
The exact cues triggering the annual phenomenon remain unclear, but it is believed to be linked to water temperatures as well as the lunar, tidal and 24-hour light cycles. Scientists’ observations indicate a strong connection between the coral spawn and seasonal lunar cycles. This year full moons fall on Saturday, Aug. 23, and Monday, Sept. 22, so divers can make reservations with local dive operators for coral spawning night dives Aug, 22, 23 and 24 as well as Sept. 21, 22 and 23.
I wish I hadn’t just come back from vacation, or I’d be booking my trip now.

Hi Jeff…
the last year I had a coral spawning into my tank… it’s an incredible thing!
My Acropora microphthalma has spawned tons of eggs (or planulae).
I think that, aside some minor problems for the tank, it’s a joy that every keeper of reef aquarium has to feel in his life.
Danilo
http://www.DaniReef.com
I agree. I had some acro spawn without me noticing. All I saw was its replicates in a couple of places in the tank. Plus, the eggs are food for corals and fish.. yummy!
That would have been fascinating to see. You get any photos of the event?
Yes of course
Take a look here:
http://www.danireef.com/2007/08/03/riproduzione-sessuata-di-acropora-microphthalma/
Danilo
http://www.DaniReef.com