a 6'x30"x30" can fairly easily be taken down the most ackward of stairwells, you just need to rent a fridge dolly, they work great! A tank can go anywhere a fridge can go, and a fridge can go down any stairs imaginable, even spiral stairwells. It looks impossible at best, but it is fairly easy to do with 2 people, more makes it even better... I have moved lots, they can take alot of abuse....