[youtube width=”670″ height=”410″]http://www.youtube.com/watch?v=LhHmRvhrOl0[/youtube]
This video of Small Polyp Stony Corals from a macro point of view is an excellent example of what good water flow and polyp extension looks like. If you have an SPS coral tank and your corals extend their polyps this much and they flap around in the flow to this degree, then you’ve probably got your water flow pretty well dialed in with some gyres, alternating motion and good mass water movement. If you have SPS corals and their polyps don’t flap in the breeze like this, consider the reasons why your corals have limp polyps. It is perfectly normal for SPS polyps not to open up during the day due to coral-nipping fish, as in the wild, but what is most important is that you have ample water flow to help the biological processes of your corals and the reef. The movement of the SPS coral polyps in this video is essentially a good benchmark for how much water flow is ‘ideal’ for many fast growing stony corals.