Depending on how much of a rescape you are doing. Since you have your substrates for over a year, those aren't dust. They are just simply mulms and debris and waste trapped underneath it. Regardless what substrates you use, a major rescape will stir up tons of debris. I say leave the substrates alone. Rescape as you please and try not to dig through the substrates too much.
This is what I would do. Get a 15g or 31g square storage box from Lowes or Homedepot. The 15g is about $7 and the 31g is about $15. You can also get a large 29g round plastic garbage can. They cost more, something like $30. Fill them up with your tank water. Use your head now...the square one it would deform a bit when the water is pretty filled up. So, don't fill them up too much. With the round garbage can, you can fill it up higher. Put your fish in there as well as your filter. Keep the filter running in it. Then, drain whatever the water level needed to enable you to move the tank. After you are done, put fish and the old water back to the tank, and followed by filling up the tank new water. Next day, do another 40% water change. After your rescape, you would experience a spike in your ammonia level. Your may experience a sudden outburst of algae. Doing one or 2 40% WC after the rescape should help.
Last edited by tetra73; 08-02-2013 at 06:16 PM.