A large fish tank of 55 gallons or more is heavy even when empty and enormously heavy full, so it demands extra hands and careful glass handling. As with any aquarium, the water, fish, and substrate all travel separately, but the sheer size raises the stakes: a big empty tank still flexes and its silicone seams can fail if it is lifted unevenly or set down hard.
Pro tip: Use lifting straps and a dolly. A large empty tank is still heavy and awkward for even three people.
Watch out: A full large tank weighs hundreds of pounds and will crack. Always drain it completely first.