[piercho]

Algae scrubbers are a sub-group of plant filters in the "natural" family of reefkeeping methods. The Algae Turf Scrubber (ATS) was a concept for filtration developed and used by Walter Adey of the Smithsonian Institute and explained in his book Dynamic Aquaria. Basic parameters are a surface for growing shallow-water turf algae, strong illumination, control/elimination of grazers in the scrubber compartment, and surging water (wave action) across the turf intermittently exposing the turf to water then air. Turfs can grow extremely fast and the turf must be harvested frequently (typically weekly) to keep the turf at optimum productivity.

A particular type of ATS designed by Adey with the dump bucket (for surge) combined with the turf growing surface was patented and marketed, without great success. There have been commercial varieties of algae scrubbers sold that don't meet all the parameters of Adey's ATS: A very expensive algae scrubber using a revolving wheel for the algae growing surface and air-powered water circulation called an eco-wheel was sold for a while. Currently a vertical algae scrubber that has no surge but flows the water down through turf algae growing on a hanging screen has gained some devotees.

Suggested search strings:
Adey
ATS or Algae Turf Scrubber
Eco Wheel or eco-wheel
Santa Monica

Reading:
Dynamic Aquaria, Adey and Love
The Reef Aquarium Volume Three, Delbeek and Sprung
The reef tank of the month for March 2012 incorporates a slanted algae scrubber that flows a thin film of water across the algae growing surface.

My experience is that a "true" ATS is much more effective for nutrient removal than a refugia with graze-resistant macro-algae. The surge, however, is difficult to achieve and the additional maintenance due to salt spray is not trivial. Different varieties of algae scrubbers that aren't "true" ATS may be worthwhile but I haven't used them myself.