Test your new water for PO4
and nitrates also. Unless your using ro
water there is a chance that your filtered water is not removing it all.
you need to find the source and then go from there, test new water if thats not the source how much and what are you feeding. If you can't track down the source then you can use a phosban reactor or some other PO4
remover. What are the numbers for your PO4
and nitrate now.
I would remove as much of the CC as you can, covering it with sand will just hide it for a while, CC always finds its way backup to the top.
Stired things up how? By removing the CC or doing a vac on what it left?
Test you filtered water and post numbers.. You can have 20 filters and still have crap in the water. What are the filters? Just micron and carbon?
Add no new fish or inverts till you get things running better and learn more about the hobby.
This is a great site to learn and we are all here to hepl out.
Which corallife skimmer?