Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Seaweed cultivator
Seaweed cultivators (the devices) are just now becoming available to the public, mainly because of the LED (light-emitting diode) which has made low-cost, reliable, and waterproof illumination sources (especially in the red 660-nanometer spectrum) feasible. Seaweed cultivators are an offshoot of algae scrubbers, which were developed to filter aquariums. By replacing the aquarium with a reservoir of fertilized seawater, a stand-alone cultivator becomes possible, and even a desktop cultivator is possible if the size is small enough or if the reservoir is placed beneath the desk.