To clarify... nitrate levels don't matter until I stock the tank? I am thinking that the nitrate levels may get CRAZY high if I can't stock right away and have to keep feeding the BB. Should I worry about that?
I know that I need to do a big enough water change (or multiple changes) just before stocking to get the nitrates as low as possible.
Correct - many people end up with nitrates off the chart - a large water change or two - (or even draining your tank and refilling it if the tank is small enough) can bring em way down to a safe level for new fish.