i just recently moved from my apt (2nd floor) to my new house and also had a 75gal. remember that the gravel will slide to the end that is going down first making it even heavier for that person. might want to take it out.
I moved my 75 gal & stand up 3 flights of stairs. Of course, it's acrylic. The 125s I can't move by myself up or down stairs. I've been planning on getting a stair-climbing forklift like this: