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Italiano29 Mar Nutrition, Growth and Maintenance of Corals, Zooxanthellae and Phytoplankton
Corals Nutritions: Corals are mixotrophic organisms, they feed autotrophic by means of zooxanthellae, and heterotrophic, with the help of phytoplankton, zooplankton, bacterioplankton or food provided by us, using direct methods such as providing chopped shrimp, fish, shellfish obviously the right size according to the polyps, or indirect methods such as the use of funds colonize by annelids and small crustaceans. Another indirect method is to create the so-called “refugium”, a tank connected with the main aquarium, where there are no predators, no excessive movement of water, with the presence of specific algae. The correct nutrition is therefore a balancing of amount and timing, between autotrophic and heterotrophic nutrition, usually during daylight hours autotrophic, and during the dark hours heterotrophic.
Zooxanthellae: Zooxanthellae are photosynthetic algae, unicellular microscopic in size (about 5 microns) that live in symbiosis with many species of coral and are localized in the tissue exposed to light. They live in symbiosis with the coral polyps because they get from those nutrients such as phosphates, nitrates, carbon dioxide CO2 and thanks to photosynthesis, triggered by the presence of light, are able to produce the molecules needed to the nutritional needs of the coral, providing oxygen and carbohydrates. Zooxanthellae, thanks to a high concentration of pigments such as chlorophyll and carotenoids are also the “responsible” of the different colors of corals. That colors are more effective under water where the concentration of blue and green light is higer. In aquarium, usually they make 60-80% of the energy of coral needs, that’s why is required a strong illumination, but be careful because in some cases excessive exposure to light can cause intoxication of excessive production of oxygen.
Phytoplankton: Phytoplankton is a autotrophic photosynthetic organism present in the plankton and using solar radiation as a source of energy. It is located at the base of the food chain in most aquatic ecosystems and plays a vital role providing the material and energy flow necessary for the maintenance of heterotrophic organisms. Unlike what is often believed, phytoplankton is not much used by calcareous skeleton corals (sps and lps), while it is essential for the sustenance of soft corals, Zoanthids, Gorgonians and aposimbiontic corals, those who do not have zooxanthellae, are the ones in the aquarium they necessarily need service daily to survive, can not count on any photosynthetic symbiotic algae action.
To cultivate phytoplankton, we can use ordinary plastic bottles, putting them in front of two or three 20W neon, not less then 15 hours a day and airing the bottle with a bubbble tube without air stone, posizioned on the bottom of the bottle, with a moderate power, we can use olso special kits. Be careful of external contamination! The water inside must be chlorine-free, with a pH not less then 7, a GH at 10, and a temperature of about 25 ° Celsius. You will add chemicals elements to promote growth. The proportions are about 20-40 cc of phyto in 1 liter, and after 10 days you will see that it is ready by dark green, at this point we can use our phyto to feed the zooplankton. The most popular algae are: Nannochloropsis, Isochrysis, Tetraselmis, Chaetocerous and Chlorella.
Some things to see if you are feeding well your corals; if the coral will darken, in conditions of optimum water values and proper lighting, we must increase or change their diet. If the polyps are retracted and the corals lose tissue or takes a quick whitening it is possible that there is a wrong or limited heterotrophic nutrition. Then replace or supplement immediately.