live sand

Do you have to use live sand? or can it be just a regular substrate? Thanks in advance

Okay, this is a very newbie question as I've always had freshwater before. I received my live sand today, and my salt, and my RO unit. It might take a day or so to get the water I need. In the meantime, can I add the sand? Or do I need to wait until the water is ready to go in so it doesn't...