An apparatus for macroalgal attachment in an algae scrubber or seaweed cultivator comprising a set of discrete non-connected appendages extending from a support member such that the appendages receive water flow and illumination so as to cause macroalgae to attach to and grow on said appendages, whereby said macroalgal growth can be comb harvested to provide useful biomass or to remove nutrients from the water. Attachment textures and growth compartments are also claimed.
