tank water is pumped into the inlet on top , runs down on the mesh and with the led's on you grow algae on it and not on your DT. on the processed you scrub nitrate and phosphates from your water, once a week the mesh is clean . IMO this is better than a refugium.
I was reading a thread about a Scrubber System on RC. Check it out, great read. The manufacturers claim you don't need to do water changes or have a skimmer. The scrubber does all the work.