If all you have is sand and water, putting in uncured rock is ok. I purchased 50lbs of fiji live rock fresh in the box from jeff, and it was chock full of life--nice macroalgae, polyps, sponges, a small spiny oyster (!), some encrusting SPS, tunicates, and most importantly, no aptasia! But, as with all things your mileage might vary. I think that if you get the uncured rock straight from the box it was shipped in from Fiji you'll end up with more life on it. Good luck!