nes999, You might try an appliance dolly with your moving your 500 gal. tank down the flight of stairs you mentioned. One of you at each end. If you have to rent one make sure it has a hand brake on it before you rent it. If you cant find an appliance dolly, get a regular hand truck with a hand brake on it. Having a hand brake on the dolly/hand truck, will make it easier to control the speed going down the stairs. I know this may sound far fetched to try and locate, but believe me, I moved a 250 gal. by myself down a couple flights of stairs and having the hand truck with the hand brake on it, made it 5 times easier for me as I controled the deceleration speed of the entire trip. I was truly amazed. My tank never suffered any repercussions from the move either. No leaks or cracks. If you can't find one of these appliance dollys or hand trucks, send me an e-mail. I'll try and remember what company I rented from when I did mine, and I'll recontact you on this thread. Good Luck w/your move.