Here is a link to Part 1 of the article. Its 5 parts in total.
http://www.advancedaquarist.com/2006...ew?searchterm=
"We take for granted that we have very specialized breathing structures: our lungs are internalized and actively create favorable concentration gradients by forcing air into narrow passage ways so that we can breathe properly. Fish have external gills, crustaceans have internal gills, insects have trachae and even nudibranchs have external branchae. All of these structures feature a very high surface area and a good deal of vascularization. Corals, on the other hand, have no specialized respiratory structures. Their external anatomy only features tentacles, a mouth, some tissue in between the polyps and, in the case of soft corals, they also have some pinnules along the sides of the tentacles. None of these are differentiated into specialized respiratory structures even though they have to rely on these anatomical features for gas exchange. If you had to breathe (respire) as a coral breathes,this would be the equivalent of holding your lungs outside of your body, inside out, and just hoping that the wind would blow hard and long enough for you to be able to breathe. This is how corals breathe in their environment and the scenario above illustrates the importance of water flow for adequate gas exchange in corals. This perspective might make you think twice about reducing your aquarium's flow at night."