ok so my new(new to me) tank came in the mail yesterday, and when i was at home depot getting some longer screws for the cradel i stumbled upon a white knob. It looks exactly like the on off knob on the tank and the one i got is sorta dinged up so i spend the $.97 to get it. Now here comes my question, how do i get the old one off? i would post some pics but im at work and the stuff/camera are at home.