Either choice will work just fine.I have the original grade which is sugar size with some pieces of shells that is bigger.Like Yote mention,oolitic is very,very fine sand that can get blown around by the current.IMO there is nothing wrong with using the live sand.There is nothing wrong with adding as much live bacteria as possible when first setting up a system.The price difference between the Carib sea live and dry sand is negligible.Nothing wrong with going even 20% live,80% dry too.