Well, if you want good advice, you might want to start a new thread since this is buried in the 40B dimensions thread.
But not to worry, I am here to offer my "never before done" guess and speculation advice...
You could always get new sand and seed it with your old. It's not that expensive when compared to everything else, you could get away with a single 40lb bag and seed it. Maybe $35 for dry aragonite using a CMAS discount. Its going to be tough though if you use your existing sand, I'd keep any fish in a quarantine for a while and have enough saltwater made and ready for water changes until you see any cycle finish, which should happen fast. Then again, you might not see any cycle, just extra released nitrates. But still, keep the fish away if you can to remove a bit of stress while your levels readjust.