Recently I had the opportunity to visit the Shedd Aquarium in Chicago. Behind their Wild Reef exhibit - which is a must see - there is a tank of about 500 Gal or so and an area where they are propagating staghorn corals and soft corals. The tank was extremely impressive. As part of the filtration system for this setup was a waterfall algae scrubber. - the light to drive it is the same as over the frag propagation area.