I must disagree with Reefman on this one..Changinmg to Live sand will make a BIG diference in your tank,As long as you go with 3-4 inches.Also DO NOT MIX the sand and CC.The sand will make it's way to the bottom,thus eliminating any benafits of having it.And lastly,By Just adding sand to an existing setup(as per reefmans post) there will NOT be a recycle.A recycle would occure if you were to remove the CC,Then replace it with "DEAD SAND".But if using live sand,ALL LIVE SAND,There will be no recycle at all...