Lighting suitable for a marine tank will almost always be too much for a planted tank. For example, an 8 tube T5HO light will grossly over light a planted tank, unless you hang it high above the tank, with lots of spill-over. Fortunately that dimmable ATI T5HO light can be dimmed down enough to make it usable on a planted tank. But, running just 4 bulbs will make it much easier to do so - using only every other bulb socket set. I think that would be your best choice, since you already have the light fixture.