With two fixtures you should be ok, but the sides or some part of the tank will have less light than the centers of the lighting. On the other hand, 3 seems to be too much. lol Maybe if you get a light with optics so it has a good spread? Or you could hang them up just a tad higher to get the spread you'll need. You are looking at quality fixtures which you most likely wouldnt run at full anyways so bringing the fixture higher up could be the solution.