Lol - I meant an empty one ha ha. A four foot fish tank can make a good hamster habitat but you'd need a lid making out of mesh and wood. I prefer cages anyway - not just for the ventilation but you can do a lot with them and attach things to the roof and bars, and access tends to be better for interaction.
Have you got a cage yet? If not Zooplus is a good place to look. The Barney, Alexander and Alaska are all good and popular. Also the Savic Hamster Plaza
Hamster Cages | great selection at zooplus
http://www.petsathome.com/shop/en/pe...r-and-rat-cage