2" of live Halimeda. This is a green calcareous macro algae that grows at the bottom of the reef. This plant is usually used as a decorative plant in display tanks but also does well in refugium. These macro grow in from end to end forming a chain like structure. Halimeda requires sufficient Calcium so make sure to test your Calcium level weekly to find the proper amount of Calcium to dose to keep these macro alive and happy.