I wouldn't recommend you get one at all. How many other reptiles do you have? Do you have previous monitor experience? Based upon your english I would be willing to guess you are either young- and this is a bad pet for you. Or you are uneducated/foreign and too lazy to do basic research for basic spelling so you can get the name right.
Frankly, there are a lot of places online that will tell you fish tanks are awful for monitors, and none of them will work for keeping a monitor. Hell there's a thread just a couple down explaining why fish tanks are bad. If you can't do that kind of basic research into the possibility of owning a bosc. You aren't ready for one.
