Hey, crushed coral will be fine for FW, but you have to be careful because it will raise you ph on you. But you are right it is sickenly expensive. As for the sand, I was kind of in a jam, the guy I bought that tank from decided he wanted to keep his substrate... so I had no time to do anything, clean the sand, let it settle, nothing, because I had to get the fish back into the tank pronto. All I did was put the sand in the tank, put a glass plate on top of it and slowly poured the water onto the plate, I was expecting it to be severly cloudy, but I was shocked that it wasn't at all. I may have lucked out and got super clean sand, but I think the real key is to just add the water gently as to not upset the sand too much.
