Live sand that's shipped will likely have some die off. Live rock from someone else's established tank should already be cured and not cause much (if any) of a cycle. If you put a fish or two in, they'll produce ammonia, which will cause the tank to cycle. Animal waste and dead/decaying material (sponges from live rock; fish food; etc) causes a cycle in your tank until it can build up enough bacteria to handle the ammonia (first cycle) and the nitrate (second cycle). Where are you in Mt. Juliet? I'm off Division, west of N. Mt. Juliet road. Certainly willing to help if need be.