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					Originally Posted by Acrowhora
					
				 
				and they seem to be covered in sand. 
			
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 Since the water went cloudy after the water change and you say there seems to be sand all over the corals I would suspect that there was an imbalance in the Alk/Ca and some precipitation happened. 
Other possible causes of cloudy water are bacterial blooms and spawning events.
Recommended course of action would be water changes and test your Alk.
Cheers,
Tim