Halimeda are green calcareous algae found worldwide and used as decorative plants in the marine aquarium. Various references will place Halimeda in the Halimedaceae, Udoteaceae, or Codiaceae family. The irregular oval segments of Halimeda appear as several small green coins glued from end-to-end, forming a chain. For this reason, Halimeda may also be called the Money Plant. Calcareous algae deposit limestone (calcium carbonate) in their tissues. When the algae dies, the calcium carbonate is left as sediment in tropical lagoons and reefs.
In the wild, the Halimeda grow in thick clusters that can range from one inch to several feet in diameter. Halimeda are generally hardy in the right conditions, and few fish will feed on them. In addition to light, they require sufficient calcium to grow. They are not as tolerant of high nitrate or phosphate levels compared to some other algae. They also do not tolerate extensive pruning.