Ive never had a tank with lights that were short. Ive always got them the full length of the tank. I guess I will see what its like and decide from there. I could just replace one of the 36" with a 48" and still get a little dark around the edges. That would give me 7' of lighting on the 8' tank.I kind of like the look of dark spots towards both ends of the tank. I took the 4ft off the 150 and am using a 2ft. Much smaller tank than yours though