Removing Dead algae

Hi. 3rd season with 10,000 gallon semi-Inground. My do chewed through the cover over winter allowing a lot of organic matter to mingle with the pool water once the ice melted. Water was black upon removing cover. Have shocked with 2 bags of HTH twice. Water is much better. However, cloudiness remains. Been running sand filter almost non-stop for a week with very little improvement. One of the tips on poolsolutions.com says removing dead algae with a sand filter can be very difficult. Any suggestions? Thanks!