Those particles might just be microbubbles coming from your skimmer or air getting into your return line? I had this happen with my skimmer a few weeks ago. Fixed it by wrapping an open ended sock around my skimmers outlet.
I get particles in the water column whenever my goby decides to dig a new home, which is like once a week
powerheads could be kicking up excess detritus that's collecting somewhere? Do you have large fish? When they poop it is messy!