I'm not saying to use the filter socks because of micro bubbles. As a matter of fact that isn't a reason IMO to use a filter sock. I'm suggesting a filter sock to catch anything that might be floating in the water. The sock will catch it and collect it for your removal. If it's dust, a 100 micron sock should work well.
Did anyone do any housecleaning near the tank? Maybe stirred up some dust and it went airborne? Just a thought.
Someone else mentioned that it might be sand from a misdirected powerhead?
Again, a filter sock can contain any of these things to help clean up the system. That's why people use them.
I have the same exact thing going on in my tank. It started yesterday a few hours after I accidentally popped a green bubble algae ball so I'm thinking mine is because of that. Were you moving anything around in your tank when it started?
I've seen this activity in my prior tank as well. It's like a spawning of some sort. Not harmfull by any means. Strom the tank more often and it will go away after several days (that's if it is what I think it is, lol). Btw, do you see it on the some of the rocks more than others ? In my experiences, I had shortened the day cycle to acclimate coral when I noticed these white floating things everywhere. Observed the tank for awhile and noticed that it seemed to be coming right out of the rocks :-0. I did ask around to see if anyone has had something like this happen to them too. Some said never and others said it was a spawing of some sort.