In my experience there is no easy way to get rid of that fine silt. Eventually it will settle and people claim that when bacteria start to inhibit it it will get heavier. When I set up my 75 gal, I had the same problem - used filter socks and canister filters and thought the problem went away. Then I got a sand shifting goby and the cloudiness just returned. I got so sick of it, that I put all the corals, rocks, and fish in buckets, saved as much water as I could and pulled out all the sand, rinsed it thoroughly with a 5 gallon bucket and a garden hose then put it back. I never had the problem again nor will I ever add sand again without rinsing it first.
Id suggest you drain the tank (save the water) pull out the sand and rinse it properly. It will be a continual headache otherwise.