Try a polishing pad. I put a dual density padnin my sump pink one from eBay and it took all the ditruis and fine particulate out of the water in 8 hours,
It slowed my sump flow so much, I almost overflowed dt.
Drain could not keep up wit return.
The water was up to edge and cresting....
Grabbed siphon and shut pump
Pulled 3 gallons off top.
Put in a fresh filter and dialed down return pump a bit
It was a good thing I was at tank b4 it got messy...