i already have a piece of foil on top, its covering just enough of the top so that the heat lamp is open. then at night, i slide the foil over to the other side and turn on the blacklight. i just cannot keep the moisture up at all?? definately cant keep it steady. i can try to cover the top a little more, but if i go much further, the light will be covered? i have to mist the tank about every hour to keep it at 50%.