I mean I understand corals like zoos maybe excreting a slime coat...but what about acros?  I hear how they may be harvested during low tide...so how do they not just dry up?  Do they excrete slime as well?  Does being exposed have any benefits?  I would imagine that it would take care of certain pests like acro crabs and maybe some parasites?  
Just wondering fellas,
-MatthewM
				
			Just wondering fellas,
-MatthewM