I used crushed coral in my filters for my African tank, and coral rock decorations, as I keep my pH raised and buffered with it. I do not have problems with cloudiness, but there is a sandy debris that accumulates, which is fine because I have buffering sand in there as well. If you have kept SW
and would like colorful FW
fish, there are many Africans that rival the beauty of SW
fish, so this might be a way to go. If you already have hard, alkaline tap water it is easier to keep Africans, as well.