When i kept Andy in a tank with a screen lid, i had the light resting right on top of the mesh without any problems. You just have to make sure you dont put something flamable close to the light. As far as wattage goes, that will be something you need to experiment with. The temp in the room where your bp is kept, the amount of air flow around and through the tank, and the length of time you leave the light on will all be determining factors in the wattage of bulb you need. You'll probably need to experiment with different wattages until you get it down.