Looking at the tank are you sure this is freshwater gravel? It looks like the crushed aragonite that petco sells which should work fine
This is the current substrate
Agree. Don’t do any coral until all this is fixed. It’s throwing money away and the coral loss will negatively affect the tankI wouldnt do coral yet, the light you have wont support their growth. THat light is better suited for a fowlr (fish only with live rock)