1. Being oxygenated will not kill denitrifying bacteria.

2. Bacteria will reproduce quickly to compensate. This can happen within days. You will just go through a very brief cycling period.

3. Your problem is going to be from stiring up the nutrients trapped in your sand. Expect and plan for a algae bloom after moving to the new tank.

4. Lights depend on what you are planning on stocking your new tank with. SPS and clams - MH, anything else, fluorescents (VHO, PC or HO T-5s). MH may have a higher initial cost, but are cheaper when you consider the bulb replacement costs on a per watt basis.