Depends on where it's moving, and what the tank is made of. If it's acrylic, 2 people no problem and the only possible issues is sharp edges of the acrylic corners. For a glass tank - 2 people can be enough as long as they're somewhat able bodied, and there are no "acrobatics" needed to move it (this usually translates to stairs) because 2 people should be able to lift it (unless it's a crazy 3/4" rimless jobber) with suction cups onto a furniture dolly, then you can wheel it into position, and two people should be able to lift it from the dolly up. Again these are somewhat capable people doing it. if you have a lot of walking path then 2 people on each side each with a suction cup does make it a lot less work on people.