It'll work to light the fuge up....But it may not work to sustain macroalgae. Plants, (and corals), need particular wavelenghts for photosynthesis. There is some rumors of LED lamps that may come out in the next couple years that will be able to replace VHO/PC, etc... but they're still pretty much in the developmental stages. I haven't heard of anyone using LEDs as grow lights for any type of plant yet, so it may not work. I'd give it a shot and see what your growth is like, but I'd keep a close eye on it and have a place and lamp picked out to replace it in a hurry if it looks like the macro isn't doing well.
B