[tang daddy]

Use a gravel vac to sift out some and leave half an inch or sand, then dump new rinsed aragonite or crushed coral above, my tank has a mix of both and lots of flow from 2 vortechs. If you have enough heavier substrate ie. More than the lighter stuff the sand will sift to the bottom. Suprizingly enough the bigger stuff always stays at the top and the finer at the bottom. The reason is because the lighter stuff is also smaller so it settles on the bottom easier.

And I crashed my tank last year After pulling some sand out to help a member that was looking for some live sand. A costly $6k in sps and clams down the drain. Rookie mistake I will never make again....the sand was in my tank for less than 1 year but obviously when I disturbed the sand the clams all died inturn killing my sps. Most of the softies and some montis made it tho.