The most recognised representative of the macro algae, among aquarists, are representatives from the Order Caulerpales . There are many species available in the aquarium hobby. Saltwater hobbyists who want the look of plants in their tank usually turn to members of this Order. They require additions of iodine, iron, calcium, and a few other trace elements. Frequent water changes are usually sufficient to provide adequate trace elements for their needs.
Light is also a major requirement.
They utilize a lot of the blue spectrum, but also require a few other wavelengths. Flourescent lighting is usually sufficient. Members of this order can be found in many beautiful forms. Another representative of the Caulerpales is the Genus Halimeda . Halimeda is a little different in its water chemistry requirements than most macro algas.