On the initial question, I agree with everyone else. You should vacuum the substrate during the weekly water change, replacing the removed water with fresh, conditioned of course (dechlorinator, or whatever you need in your situation). The "old" water is not good for fish, no matter how much detritus.
On the discussion of python vs buckets and tank size, I can see value in either method. I now use my Python on all tanks, including my 10g and 20g, though I must be very careful filling as they fill very fast. And I have a 75-foot Python because the laundry room tap is at the other end of the house from the fish room. Sometimes I end up almost jogging. I used to use a pail on the 10g, but gave that up after surgery last year when I couldn't lift it, and now I am used to the Python even on this tank.
Byron.