For FOWLR, lighting is more for viewing pleasure. Changing to T5 might give you more options to play with different light tubes but thats about it. If you do not plan on introducing corals to your tank, you dun really need to bother about the wattage of the lights. As what Bro Limpc mentioned, if you do not wish to spend too much, better dun change. Normal PL lights will suffice for FOWLR.