Live Sand

[digger]

Hi,
I'm new to to this list, and just getting back into the reef hobby after 4 years.
We're setting up a coral tank in an aquarium that has been dormant but running for the last couple years. I was hoping someone could give me some ideas on the best way to set up a live sand bed,the best sand size, and should it be four inches deep or six inches ?... I have a 33 gallon and a 66 gallon tank. In each tank I have two inches of aragonite gravel on the bottom now but I'd like to add sand to it. I bought some dry aragonite sand by the pound at AI last weekend and didn't know if I can add it directly to the gravel bed. Can I just add the sand on top or should I mix it together, and is it best to do it gradually or can I do it all at once? Any recommendations would be really appreciated. I also need to find some live sand to add to the bed in order to populate it. Does anyone sell live sand?