I also wondered about the 200 on the second floor, but figured he'd probably bought a house...

Erik, after my disaster, I'd DEFINATELY do this: Don't move much if any of your existing sandbed. You need a couple of cupfuls for the bacteria - that's it. They double every 20-30 minutes, when there's nutrition and an environment for them.

By bringing your old sand, you are bringing all of the hazards in that sand. The sand is a toxic bomb waiting to go off - seriously. That's what caused all of my problems, and I only had an inch on the bottom.

Frankly, I'd consider this, if you can: Run your new tank without a sump at first. Get your sump up and running on it's own, and stable, and then introduce it into the "loop". With 200g of water, you should be fine until it stabilizes. Even if you have to do large water changes every week, a bucket of salt is $45 and it will change your entire system once. SO much better than a tank meltdown.