I was sooooo not happy with Marco sand. The rocks are great. I will never buy sand from him again.
For the good: it is very white and looks nice. Now, the rest.
First, 40 pounds is not 40 pounds. He takes a flat rate box and fills it up. He really should sell it by volume not weight as that is how he delivers it. This works out to be a little more than 30 pounds. On my order of 80 pounds, I was missing 16 pounds and I had to complain on his reef central forum before I finally got a response and my missing sand.
Next, the sand was so very fine, it just wasn't workable in anything but a low flow fuge. I understand that he has a different or second sand product now, but the fact that the stuff he was/is selling is so inappropriate for a reef tank, I won't trust his opinion on any sand product.