For 13 1/2 yrs now, I've used nothing but NO lighting on all of my tanks. Mind you, that's "wall to wall" lamps in the hood. (i.e. 8 fourty watt NO's over my 90's, 75's and 65 are no problem to fit in, with 6 over my 55. I can, but don't have at the moment, fit 6 20w NO's in my hood for my 20g...