[Krypticol]

the benefits are the sponges and tunicates ingest proteins as well as i believe some nitrates nitries ammonia, and detritis that is fine enough, combine with a good amount of feather dusters and time to grow you should be able to take the skimmer off line, but you need anough space for them to grow, as well as time and condition to alow them to grow a large healthy colony to fully consume the tanks wastes.
apparently a large enough well set up system will begin to develop interesting zooplankton colonies not ususally found in typical Berlin type system. and Steve had several setups that he never or very rarely put any addition food into. Coral was fed by light and zooplanton/phyto and feather dusters fed by fish, algae eaters wastes and coral slime, and sponge/tunicates fed on liguified wastes. Very interesting stuff, can't wait to buy my own house so I can develop a big tank setup with this style, as i feel it provides that "scientific" display feel