The screen maybe blocking some of it out... i hope you have a reptisun 10 and not a reptiglo. As far as mounting it, its fairly easy, i just did it a couple weeks ago. Go buy a under cabinet light fixture they have at walmart for not even 10 bucks and SMALL command hooks, i bought medium and they didnt fit, so ya small. Then go home take out the bulb that comes with the light fixture, install the reptisun and dont put the cover thing back over the bulb just let it be exposed. Next you wanna put the command hooks in the holes on the back of the fixture, you put them in side ways then you can twist them to be vertical. Then all you do is stick the command strips to it and stick it right up in the tank. Just make sure your dragons are within i think its like 6 inches away from it at all times so you dont want to mount it to high or all the way to one side of the tank. Simple as that but the fixture only fits the 24 inch bulb so i hope that's what size your looking for. hope that helped!