Basically, that's all that it is. It just provides a ton more surface area than the more common "blue balls" wet/dry. In addition to the rocker you see at the website, there is a mechanical filter that the water flows into first, then there is another big block of the same "Cell-Pore" material beneath what the site shows actually lying on the bottom of the sump. As per the information on the website:
"When the filter is properly sized to the aquarium, the biofiltration media in the rocking filter element creates a starved biofilm condition as opposed to overcrowded biofilm. As a result, systems using the BioRocker have been shown to be free of toxic ammonia and nitrite, and also show a reduced level of organics and algae; a denitrator slab may be added to decrease the concentration of nitrate in the system. "
I am quite sure that there is a substanial markup, just as there is anything marked "tropical fish". It reminds me of the time I purchased a "photographic lens brush" for $10 in a photo supply store. A few days later I saw the exact same brush, made by the exact same maufacturer and it was $2.49. The only difference? It was at Eckerd's Drug Store and it was called a "make-up" brush.
They see us coming a mile away!
Thanks for the reply,