How much base rock?

You are a magician. Plan and simple lol
I am 100 percent sure that my nitrate issues were caused by the cc since I barely ever fed and used only 0 tds rodi water. A week after I switched it my nitrates went down to 0 and stayed that way.
I'm not sayin that what I did was wrong or right. Maybe my tank was just cursed.
This is my opinion and I'm sure that a lot of other people would agree with me.
If it works for you great, but it didn't for me.

This hobby is based on a lot of opinions. I do what works for me. Sand.

 

And that's totally fine and understandable. It's blanket statements that CC is bad news for reef tanks that I'm particularly responding to, ya know what I mean? I mean, as far as we know, you also had a rotting sea star in your cc that cleared out all your fauna and that's why you had nitrates (and why switching it out fixed it). I'm not saying that was your situation, just that there are a lot of variables that are not known. It may also have been that your CuC was tailored for sand from the get-go... this may be nothing more than a case of CuC husbandry. I'm not saying it is, but I am saying there is no definitive link to CC. I don't see how you can be 100% sure.