I am having a problem with what looks like a dust blowing around in the display. I am sure it is not bubbles (that problem has been solved). It is not an easy thing to get a picture of. I have a filter sock in the sump and a 50 micron pad between the bubble traps. Flow in the tank is about 4500gph. I really don't see it coming out the returns, just in the display. This is a bare bottom tank. From what I can see it is not bubbles from any of the power heads either. Any ideas?