Don't stirr up the sand bed any more, that will spike up your nitrate automaticlly. You need to find the causes first (like overfeeding,flow,lighting age,etc). I think your tank have too much nutrients, especially silica. Adequate concentrations of silica will encouragethe growth of diatoms.Feed livestock sensibly, water change weekly and place your skimmer back in service and let it run acouple weeks and see if it get any better. Oh, and adding more clean up crew would help also.
Reefing is just like cooking, all the ingredients have to be just right , except you don't have to bring the water to a BOIL...