If he's trying to get out it means he's not happy in the tank. I'm guessing it's because... it's a tank, which while great for fish really isn't appropriate for BP's without a lot of work and accessories to make it suitable. There's not much you can do about it except ensure that your temps and humidity are correct, and he has appropriate-sized hides. How is he set up? Also, what did his prior owner have him in?