It will take all night - but be happy - those damsels you have can go back into the tank in about two hours and should survive. The temp of the water needs to be stablized mostly.
these animals have lived with underwater sand storms for many generations. Mine survive three such mega storms without even losing their angry attitudes.
Just a quick comment - I would have left the CC on the bottom of the tank and just put the sand on top to help create an anerobic layer where nitrate eating bacteria could live.