Welcome to AA Freakinjimbob!
I hope you are getting a VERY large tank for that Arowana. There are several ways to do this. The hard, and the easy.
Easy: Bucket the fish individually with lots of extra water, drain the old tain, move it, put the new tank in place. Put in the decor. Then dump in the water that is with the fish, along with the fish. Then add new water to the tank. Restart the filter, heaters, and powerheads. It would be like doing a large water change.
Hard Way (the way we did it. Ugh): Set the new tank in the room about 3 feet away from the old tank. Put the water and fish from the old tank into the new tank (even though its not in its final position). Then move the old tank. Then put the water and fish from the new tank back to the old tank. Then move the new tank into it's position. Then transfer the fish and water to the new tank. It's a lot of work. But it still works. Then just add the new water and decor and you're done.
Just make sure that you use your old filter on the new tank for a while. Make sure that the old filter media doesn't dry out during the transition. And don't clean the filter for several weeks after the change.
