To play it safe, you should always cure the sand first before adding it to your tank. Curing provides a bacterial coating on the individual sand grains so the clouding will dissipate in a few hours instead of a few days. Here's how:
Put the sand you are wanting to cure in a large rubbermaid container or several smaller containers along with some saltwater.
Add a small powerhead for circulation and a small heater.
Add a few pinches of flake food to get the cycle started.
Cure it for a few weeks, stirring the sand daily so that all the sand gets coated with bacteria.
Add no more than 1/2" of sand over your existing sand per week until you reach your desired sand bed depth in your display tank.