I believe that it would have to be a fairly large Mantis to break a tank. They DO pack a hell of a wallup though. Mine is about 1 inch and he hit me, no blood or bruising, but if he was bigger, I could see it cracking glass. Everything I have read about them says they strike with the force of a .22 cal. bullet. Speed is an entirely different story, they are VERY fast, but not as fast as a bullet. Mine just kicks back and watches the outside world from his favorite hole in his rock. When he starts moving around, I feed him various foods. They are pretty cool!
Bill