I agree to a certain extent that removing LR won't actually reduce you NO3 levels but it certainly can help.However,to much LR and/or a poorly designed aquascape can have disastrous effects.The points that Angie made are valid and should be taken into consideration.Dead spots that form from too much LR or pileing it up will be the perfect spots for nuissance algae to take root.Most of use don't have near enough water movement in our tanks as it is.A small,open aquascape that doesn't rely on the sides or back of the tank for support makes it easier to provide water movement.
IMO,less is often better when it comes to amount of LR in a reef tank.Aerobic bacteria and anaerobic bacteria populatios will balance out with the total availiable nutrients/Nitrogen that is availiable to sustain them.So,you could just as easy have 50lbs of LR being used for bacterial filtration in a 75gal tank as 150lbs of LR.The bacteria densities will be much higher in the 50lb Lr than it would be in th 150lbs.We havn't even talked about the wonderful Nitrogen processing capabilities of a sandbed which ALONE is capable of maintaing a lightly stocked reef tank.