[GoFish]

If I was you I would siphon it out when doing a water change... If the crushed coral is too big for your siphon hose than you could use a larger diameter one (pick out the largest pieces by hand). If there isn't enough suction to extract the larger pieces than I would try to have the draining end of the hose as low as possible. If you're in a 2 level house then use a longer hose and drain to the lower floor. The lower the hose, the more suction you'll get, might take 2 people, one on each end of the hose.
You're probably gonna find a lot of detritus hidden in there so you'd probably have to finesse with the end of the hose to pick the crushed coral up while leaving the sand behind. I usually pinch the hose between my thumb and forefinger to control the amount of suction, I use a clear vinyl hose. If it stirs up a lot of detritus hidden in there and you can't avoid clouding the water then I'd consider doing this over the course of a few or more water changes doing sections. Your sand is probably gonna be pretty gross. Maybe consider taking the sand out at the same time and go bare bottom? If you don't like the looks then at least you have the sand out so you can rinse it and put it back in?
Or maybe someone else has a better idea? Best of luck