In different parts, we’d like to show some basics on the often discussed theme of coral-feeding. Have fun with part 1!
Most of the SPS and LPS corals except some azoo-corals primarily live by sunlight. Corals that are mostly living in shallow do this by implementing unicellular symbiotic algae into their structure. By doing photosynthesis, the resulting sugar is then used as an energy source by the coral.
In their natural environment, corals are mostly established in very low-nurtrient water – but, like most algae, the symbiotic algeas need somewhat higher nitrate and phosphate levels to survive. So over the millions of years, the corals developed another source for energy – the coral polyps that can actively catch plankton, which is mostly micro- and zooplankton.
And: They have to! Growing in even in deeper regions with less light and a very low nutrient level, the corals are not able to keep the zooxanthellae concentration reasonably high and thereby generate enough energy. In addition, corals need phospho-lipids, carotenoids, vitamins and many other organic compounds which they can only get by catching plankton. Zooxanthellaes cannot produce these substances for the coral.
Therefore, corals are mixotrophic organisms – they can use, depending on the offered source, autotrophic and heterotrophic food.
And what about our reef tanks?
Many saltwater aquarists know, that SPS corals show the best colors at now nutrient values and strong lightening. This has to do with the fact that at low nutrient values, strong lightening and a good flow the zooxanthellae concentration is not that high. Zooxanthellae normally have a brown color and are fertilized by NO3 & PO4. A high density of zooxanthellae leads to brown looking corals. With a low density of zoocanthellae the coral is not covered by the brown algae so that the colorful skeleton becomes visible.
By keeping the phosphate and nitrate levels low, SPS corals show the best bold colors. But, just in the use of strong adsorbents, the coral lacks the necessary energy source from the photosynthetic products of the zooxanthellae. The saltwater aquarist is adjusting the nutrient levels to those of the natural sea.
But: The microfauna and zooplankton for alternative food is mostly missing in modern low-nutrient-tanks. And therefore an active feeding is necessary. So, a modern mixed-LPS/SPS reef tank needs the following:
– Strong lightening
– Strong and changing flow
– Low nutrient levels
– Provide of coral food
The next part will focus on the different plankton species and will show a practical example how to feed SPS and LPS corals. Stay tuned!
Kindly supported by www.reefcare.de
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