“Feather macroalgae” usually refers to marine macroalgae with feathery or fern-like fronds, most commonly species in the genus Caulerpa.

Characteristics:

• Bright green, feather-shaped branches.
• Grows in saltwater aquariums and tropical coastal waters.
• Can help absorb nutrients such as nitrate and phosphate from the water.
• Fast-growing and often used in refugiums for nutrient export.

Common examples include:

• Caulerpa sertularioides (feather caulerpa)
• Caulerpa taxifolia

In aquariums, feather macroalgae can be beneficial for water quality, but some species may spread aggressively and require regular pruning.