The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
Pass on the CC, it looks nice but over time it will need to be cleaned on a regular basis and will trap waste, breaking down into nitrate.
Go with sand...... 2-3 " is fine. Large stone what type not all stones can go in SW set ups.
i would empty, clean and refill tank with new ro, ro/di water.