Depends on the kind of background you're going to buy. Normally the size is on the package so you can check/measure if it will fit. If you gonna take a standard juwel background, you most likely will have to use more than 1 pieces. You also have bigger backgrounds that will fit in 1 go.
You have flat 3d backgrounds which you can glue to the back and you have the hollow ones where, if you want, can hide an external filter and your heater behind. Although the second option in most cases is more expensive, I do like them better. The second option is also glued in place
Another option is to paint the outside of the tank, or put a foil of some sorts on there for an even color. The LFS (local fish store) also have these posters which have a picture/scene on them so you don't have anything in the tank so you don't 'lose' any liters of water to have a nice background. Another advantage; they don't get dirty so you don't have to clean them
That said, it is a nice size tank. Any ideas what fish you want to keep in it?
