I set up a 65 gallon saltwater with live rock about a month and a half ago. In it there is about 50 lbs. of live rock, 40 lbs. or live sand and 30 lbs. of aragonite. It's a deep sandbed as I eventually would like to put a pair of jawfish in. Currently I have two yellow tail damsels and three small engineer gobies for cycling purposes, I may get rid of the gobies if they get too big. Well recently I noticed a brown dusting over the substrate, the live rock, the glass and floating on the surface. From what I could find on the internet it said that it wasn't completely cycled and that upon completion of cycling it would eventually go away. Is this true? Is this something I really need to be worried about? The fish and snails are all doing fine. Ph and Salinity are right on the money. Anybody have some answers for me. Much appreciated.