Caulerpa is the most common macro algae found in aquariums.

* Marine aquariums demand a variety of marine algae. 
* Algae offers favorable surroundings for, not only fish, but also microfauna, which helps metabolize food particles. This enhances the food chain: for example, the mandarin fishes will live off these microfauna. 
* Caulerpa represents an important food source for many fish. 
* Caulerpa releases organic acids and necessary substances such as vitamins and amino acids. 
* Perhaps the most important role of Caulerpa in the aquarium is to assimilate nitrogenous compounds and phosphates. Ammonia and nitrate are the most common sources of nitrogen for plants. This is the basis of the algae scrubber. The algae uses these nutrients from the water to anobolize proteins, and the result is cleaner water. 
* In many large modern public aquariums Caulerpa is raised because of it's healing qualities. Sick fish often recover quickly when Caulerpa is in the aquarium.

HERE'S WHY IT WORKS:

Various marine algaes contain medicinal substances. Several have significant antibiotic effects against fungi and disease causing microorganisims from the marine substrate. These antibiotic substances are broad spectrum and particularly useful against microbes that are resistant to "classic" antibiotics. Sick animals introduced to aquariums with dense algae growth are sometimes spontaneously healed, even after standard treatments failed. Based on the antibiotic properties, the advantages of a lush stand of Caulerpa in a marine aquarium seem to outweigh the disadvantages!