SALTWATER experts only!!!!!!!!!!!?

Yes you absolutely can. The live rock and sand should be there before fish to help cycle and cure the live rock if it needs to be. Also if your like most people you can yous small damsel fish to cycle the tank, but if your like me you can also use tail shrimp to cycle. I dont use fish to cycle my tank because i dont believe in putting the damsel in that unnecessary stress. As for alkalinity, it is essentially a measurement of water's ability to neutralize acids. Id reccomend 7-12 dKH. I hope this helped and best wishes!