Breaking smaller tanks is a possibility, but only of large specimines, and only tanks that they really shouldn't be in. If you set up a 29 or 30 gal tank you should be fine with regards to escape attempts and the tank large enough that the mantis should be happy for life. As added protection, when setting up the tank you can place a piece of acrylic directly onthe bottom of the tank then cover with sand. The bottom is the most likely place for a stomatopod to break a tank.
I haven't kept a peacock, but i like to feed my mantis just about every day, and I have assorted snails in the tank for when they get hungry. Food consists of Krill, Silversides, Cockles, scalops (basically any marine flesh they will eat). Its also a good idea to have the snails in the tank because breaking open snail shells helps keep the animal in tip top shape.
