Some suggest "curing" the sand first, building up the live bacteria. Put it in a bucket with a heater and either a powerhead or an airstone. Put some of your old crushed coral in a mesh bag on top of the sand. (Fine enough of a mesh that the crushed coral can't fall out, but water can flow through.) Add a bit of fish food, and wait. You should be able to track a cycle like when you first set up your aquarium.
When the sand is ready, put as much of your remaining crushed coral as you can into mesh bags, but leave the bags in the aquarium. Each week add the top couple inches of sand from the bucket into the aquarium. (At the same time, add another pinch of food to the bucket to keep the sand cycled.) If you add the sand all at once you'll be stuck with a huge sandstorm, and the sand in the bottom of the bucket may not be cycled as well as the stuff on top. As you start to fill in the space in the display tank, take out one bag of crushed coral at a time.