Is Feeding Corals Necessary and How Does it Benefit Them

Do you Really Need to Feed Your Corals? How Does it Benefit Them?     

     One of the greatest controversies in the hobby and a question I hear from fellow hobbyists all the time is, is it necessary to feed your corals? I use to believe it was not necessary when I first got into the hobby. After all, corals are photosynthetic. I knew and understood that some corals, were non-photosynthetic, such as some gorgonians, colt corals, dendros, etc. These NPS corals require a constant feeding since they do not host the zooxanthellae algae most other corals have to give them energy. Now, the corals that do, do not need to feed since they have the zooxanthellae algae constantly photosynthesizing and providing their host with energy right? This is false.

     Many corals and other sea-dwelling critters have a symbiotic relationship with zooxanthellae algae. This algae, through the process of photosynthesis processes the polyps wastes and produces glucose and carbon. The coral polyps use these end products of the zooxanthellae for respiration and coral growth(See Figure 1 Below). These symbiotic algae reproduce by cell division. They are yellowish/brown dinoflagellates that live within the corals polyps. The coral can control the population of the algae living within them by regulating the amount of waste for algae growth, or by limiting the amount of light and intensity by closing and opening the polyps exposing more or less algae to the light.

     Although the symbiotic algae provides energy for the corals, it is simply not enough.

     “A limitation of photosynthesis, however, is that it seems unable to provide corals with sufficient organic nitrogen and phosphorus to maintain tissue growth and organic matrix synthesis. Therefore, corals have to feed on organic material, which is called heterotrophy or heterotrophic feeding (from the Greek words heteros, or different, and troph, or feeding).–Tim Wijgerde, Ph.D

(Figure 1: The process of photosynthesis in corals and the relationship between the polyps and the zooxanthellae algae illustrated in a diagram.)

   

 

     One huge notable benefit to feeding corals is that it simply becomes a more efficient organism overall. Research shows that corals that are fed actually photosynthesize twice as much as non-fed corals do. The zooxanthellae algae will actually reproduce faster and therefore produce more energy for the coral to utilize allowing the coral to exhibit more vibrant colors and grow almost twice as fast.

     ”Research has shown that feeding enhances photosynthesis rates of zooxanthellate corals, by increasing zooxanthellae density and chlorophyll a content. For S. pistillata, zooxanthellae densities double within several weeks of zooplankton feeding, both at low and high light levels. The number of dinoflagellates residing in a single coral host cell also increases, with up to four zooxanthellae per coral cell. A higher photosynthetic capacity allows the coral to convert more light energy into chemical energy, which can be used for growth”. –Tim Wijgerde, Ph.D

     Reef Pro Coral Jama is 100% natural freeze dried zooplankton. In this mix you will find, artemia, copepods, rotifers, mysis, and lots of other microscopic critters that benefit corals in their natural environment. This is the most beneficial food you can feed your corals. Especially SPS (small polyp stony corals) such as acropora or seriatopora.

     To determine what corals feed on in the wild, researchers evaluate the gut content of corals in the wild and also experiment with the animals in laboratory. Evaluation of the gut contents of a Monastrea coral contained copepods, ostracods, mysids, menatodes, polychaetes and other zooplankton. Suspended organic material ingested by corals via sedimentary filtration included bacteria, protozoans, detritus, feces of fish, etc. Interestingly, research indicates that the scleractinian corals rejected algae and other plant material. Research indicated that even if plant material was ingested it was not digested and regurgitated. The size of prey captured by the polyps can be larger than the polyps, with the general rule being - the smaller the polyps the more important the role of autotrophic feeding. Some of the laboratory experiments were conducted using artemia nauplii as food. These are basically a form of zooplankton. The polyps easily captured nauplii of size 0.7-0.9mm. Corals with larger polyps (e.g pocillopora, stylophora) also captured Artemia nauplii up to 1.4mm. Research in predatory feeding has shown that, even in corals with polyps active in the daytime, polyps hunt more efficiently at night. -Sanjay Joshi

 

 

References

  • Wijgerde Ph. D, Tim (2013,12) Feature Article: Coral Feeding: An Overview  http://www.advancedaquarist.com/2013/12/aafeature
  • Joshi, Sanjay (2000) Feeding a Coral Reef   Aquarium http://www.personal.psu.edu/faculty/s/b/sbj4/aquarium/reeffood/feeding.html

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