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Macro algae in the Aquarium or Refugium
What are macro algae?
Marine macro algae are large-celled, photosynthetic algae that serve as the base of our ocean's food chain. They provide food, oxygen and habitat for thousands of marine inhabitants. Unlike marine plants, macro algae lack conductive tissue, true roots, stems and flowers. Instead of roots they have holdfasts or rhizoids in which individual runners support the growth between blades or stalks depending on the species. Macro algae unlike seagrasses, absorb nutrients and sunlight through their cells not the root system. The 3 main classifications of marine macroalgae are Chlorophyta (green algae), Phaeophyta (brown algae), and Rhodophyta (red algae). All of these classes also contain slightly calcified or heavily calcified algae which also depend upon high calcium levels to grow and reproduce.
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Chlorophyta (Green Algae)
The green color is caused by the dominant pigment chlorophyll, but the coloration varies between species from bright green to yellow or dark jade. They are among the most diverse and abundant group of all macroalgae representing extremely varied shapes and characteristics as well as world wide distribution.
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| Phaeophyta (Brown Algae)
There are approximately 2,000 species of marine brown algae worldwide. Most of these are cold water varieties, which include the huge kelp beds found in cold water habitats. Some tropical species of interest to aquarists that are available are Sargassum, Dictoya, Padina and Turbinaria. Of these the most beautiful and varied is the Sargassum algae.
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Rhodophyta (Red Algae)
Rhodophyta is the largest and most diverse group of tropical reef algae with more than 4,000 species worldwide. Their dominant pigment is phycoerythrin which gives off rich shades of red, orange and blue. Red algae is by far the most beautiful and striking of all marine algae and is highly sought after as an aquarium specimen.
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Why include macro algae in the aquarium?
Most importantly they offer a beautiful contrast and diversity to reef aquariums, refugiums and planted tanks. They can provide a great food source for tangs, angels and other picky eaters. Macro algae naturally filter aquarium water by reducing the available levels of phosphate, nitrogen and other waste. Overall they can enhance any marine system by providing decoration as well as shelter for many fish and invertebrates.
Natural filtration methods have increased in popularity among marine aquarists with the addition of the refugium, which provides a separate habitat for displaying and growing algae, while connected to a main display tank. A fairly new trend in the hobby has been the increased interest in creating themed ecosystems, supporting marine plant and macroalgae dominated aquariums. These systems are quickly gaining popularity as a change from the normal "reef" setup.
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Macroalgae will thrive under the right conditions and offer a replenishing food source to tank inhabitants. They require the same 16 essential nutrients as aquatic and terrestrial plants, and like most plants they need high levels of nitrogen to grow. Stability is the key to maintaining good algae growth, lighting should be 3-4 watts per gallon, ph should be 8.0 - 8.4, specific gravity of 1.023 - 1.026, water temps between 72- 85. The periodic dosing of iron and iodine can be helpful, although most prepared saltwater mixes provide this with regular water changes. Some hobbyists dose with different fertilizers to maintain lush grow in plant dominated systems, but this should be done with care, as many of these products are designed for freshwater tanks and can cause unwanted micro algae blooms. Again stability is the key, most marine algae are very tolerant of slight changes in water chemistry, but a sudden change in salinity or water temps can cause it to die off and pollute the aquarium. |
