Crushed coral is a problem waiting to happen

I'm just setting up a new29 gal tank. I have laid 10lbs of Crushed coral and then laid 20lbs. of live sand on top of that. I'm hoping the thick layer of live sand will be enough to prevent the crushed coral from getting dirty, any ideas ?
 
Eventually smaller size substrates (sand) will be on the bottom and larger substrates (CC) on top.
Although CC are not the best substrates nowdays but have done nothing but CC for s/w when other options werent avail back in the day.
 
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