Macroalgae such as Halimeda, Caulerpa, and other large celled algae are valuable additions to a saltwater aquarium. Algae and all photosynthetic creatures serve two important roles in the ecosystem of the oceans and aquariums. Light provides the energy for plants (and zooxanthellae) to convert carbon dioxide into oxygen and sugars, making it a great food source for tangs, angels, and other herbaceous animals. Secondly, macroalgae reduce the available levels of phosphates and nitrites/nitrates, an excellent form of natural filtration.
The use of "algae filters" has become popular in recent years, in part, because it is a natural approach to filtering water. The construction of such a scrubber involves simply growing macroalgae in a sump area below the aquarium or in a side mounted refugium. An established refugium can aid in the removal of pollutants in the display aquarium, so that undesirable species of algae will not grow. Many aquarists use this area not only to grow macroalgae, but also to contain live sand and live rock and raise amphipods and copepods that are found in live rock. These small crustaceans are used to feed delicate fish such as
Anthias sp. and different species of Dragonets. For best results, lighting should be provided for an extended period of time (18 to 24 hours per day). The reason for the extended photoperiod is that plants only convert carbon dioxide while lighting is available. During the dark periods, plants use oxygen and release carbon dioxide. This can result in a decline in pH, and proper buffering agents need to be employed. Excessive growth should be pruned and removed as required. Macroalgae can also be kept in the main aquarium, providing valuable hiding places along with a natural food source for many fish and invertebrates.
A Few Types of Macroalgae
The shapes and colors of macroalgae available are a benefit to those trying to find the perfect type when aquascaping or decorating their aquarium.
Hawaiian Halimeda plant usually comes as a spherical clump about the size of a baseball. This species is grown in the pristine waters of the Hawaiian Islands, and is much larger and fuller than specimens available from the Atlantic or Caribbean. It separates itself from other plants by using calcium to build a support structure within its blades. Because of this, few herbivores will feed upon this plant, giving the plant an extended lifespan within the aquarium. Halimeda is one of the hardier and slower growing of the macroalgae.
Caulerpa is one of the more common macroalgae in the saltwater hobby. This macroalgae is a favorite snack of herbivores such as tangs and angelfish. The rapid growth of this plant aids in water quality as well as filling empty areas of the aquascape. Caulerpa can be found in various shapes from flat blades, feather blades, notch leaf, and even a grape variety. In the wild, the notch leaf variety C. taxifolia has become a nuisance in the last few years. In both California, and parts of Europe, this invasive species of algae has become a major problem with overpopulation of intercostal areas. Caulerpa is usually collected from the coastal regions of Florida, where it is prevalent among the rocky estuaries.
Maiden's Hair algae provides a very soft appearance combined with all of the other benefits of macroalgae. Maiden's Hair looks like a thick mat of bright green carpet, adding an intense green color and soft flowing motion to any marine aquarium. Most Maiden's Hair is collected off of the islands of Tonga or Fiji, and comes already attached to a small piece of live rock.
There are several different species of macroalgae available to the marine hobbyist. The benefits of macroalgae cannot be understated, so if you have a marine setup, be sure to include a few of these special plants and your fish will reap the rewards.