Yeah. You took the words right offa my fingers, Cor.
Laughing Boy, you have a rather condescending tone which wouldn't sit well with anyone. And, Dr. Ron's reputation precedes him for a reason, Dan isn't the only one who disagrees with much he has to say. In any event, answering a question and jumping someone's train because you're having a bad day are two different things. You really don't have to answer any questions, and there's no reason why you have call to behave this way towards Dan, unless you have a personal beef with him, in which case it should stay personal (not be aired here).
Dan, I have to agree with Laughing Boy's reasoning behind avoiding CC, but I will take this conversion thing a bit further for everyone and offer some tips..well, one tip at least. PANTYHOSE.
Put the sand you wish to use into clean hose, and bury it in the CC. It'll look weird for a while, but after a short period of time the CC can be very easily removed without leaving a bit in with the sand. The CC, in any event, would migrate to the top of the sand, and if the bed isn't completely/deeply covered with CC there's no reason why some can't be left in.
I hope that helps anyone else who wants to replace but can't figure out how to prevent this mixing of the substrata.