Interesting indeed. Ihave had zoos, but never saw one do that.
My plate coral has an interesting response to cyclopeeze, too: it opens its mouth as wide as it can, and must start sucking water, because it soon fills with red, and it seems very happy.
There must be little swarms of no-see-ums in the ocean that get this kind of 'bonanza!' response. Some corals are certainly ready for the event.