There are also some neat non-photosynthetic inverts he could keep. These include sea squirts, sun corals, tube anemones, some gorgonians, feather dusters(any kind of tubeworm really...he could also do coco worms, or x-mas tree worms), etc. It could make for a very interesting tank!! The only objective, is constantly dripping phytoplankton into the tank, which would probably make him need to do 30% bi-weekly water changes.