Because many of you asked via Email, we combined the three articles about the feeding of LPS and SPS corals into one guide! We’d love to get your experiences about coral feeding in our comments. Happy reefing!
Basics about coral feeding
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
Zooplankton and phytoplankton
Living phytoplankton and zooplankton is the natural food of SPS. Note that there are only a few corals (eg Goniopora) that eat phytoplankton actively. Phytoplankton represents, however, a very important source of food for zooplankton. Regular addition of phytoplankton/zooplankton food promotes a boost of natural zooplankton of all sizes, which can have a very positive effect on the nutrition of the stony corals.
Here’s a video from my tank, showing many tropical mysis but also many more mikro- and makroplankton on and in the rocks (best to watch in HD directly on youtube):
Bacterioplankton and ‘pseudoplankton’:
Strengthening the bacterial flora can be supportive. Often, carbon compounds or the vodka method is used to increase the bacterioplankton. On the one hand it reduces the nutritional value slightly, on the other hand, the releasing bacteria carpets ar getting actively absorbed by the stony corals. This effect can also be observed in the use of zeolite. If the zeolite is moved several times a week, the adherent bacterial plaque gets into the tank. Also oyster eggs are ideal, because of their size and structure, and well received by stony corals.
So how do I feed my corals right?
Fact: There are more important things than coral feeding. Flow, light and low nutrient are the base of beautiful colored SPS corals. If you’re so far, that the colors and growth is good, you can start the targeted feeding. Tanks, that are on NO3=0 and PO4 = 0, basically should feed the corals because of the low supply of nutrition the coral zooxanthellae can deliver to the coral.
LPS in turn, needs to be fed in an entirely other way. Especially the popular and ultra-colored LPS corals as Acanthastrea, Scolymia australis, Lobophyllia, Euphyllia, Blastomussa and many are able to take much larger food particles – so-called macro-plankton. It starts with the small clam eggs up to the size of Artemia, Goldpods (2mm) or even Mysis. This means that, especially for a mixed tank of SPS and LPS it is crucial to have a good mix!
There is an awful amount of different food for corals on the market, and it’s not easy for less experienced reefers, by trial and error and the resulting effects or internet recherche to find out which products are good.
How can stone corals be fed the best possible way? First, a short overview:
- They prefer particle sizes between 20-50 microns (e.g. Acropora). Ideal is a a range between 20-150 microns.
- Flow is crucial. During the addition of the food it’s important to regulate down the pumps and slowly brin it up within 20-30 minutes. This enables different flow rates.
- Alternate feeding time at night and during the day, that all species get something.
- Promote natural zoo and bacterioplankton
- Enrichment with amino acid is recommended
- Cell sizes between 1500-3000 microns
- Direct feeding by pipette possible
- Copecoden, Calanus, Mysis, Artemia, and more
- Some species, such as Lobophyllia polyps extraction must provided at first (e.g. amino acids and vitamins).
What is being fed:
- 1 drop of amino acids / day on 100l
- 1 drop Coral Nectar (vitamins and supplements) / day on 100l
- 1ml NYOS Zero / 100l daily (carbon source causes a decrease of NO3/PO4 and boost the bacterial population.)
- 2x a week NYOS Goldpods and oyster eggs by using a pipette to feed the LPS directly on their mouth
- 2x weekly Reef Pepper (particle size min. 20 microns) enriched with daily ration of amino acid & Coral Nectar
Promotion of natural zooplankton
The Reef Pepper supports an extreme boost to my microorganisms and sponges that has a positive effect on the growth of corals. An offshoot in my sump with a lot of live rock acts as an additional refugium.
How to feed:
The corals are fed in the evening about 1-3 hours before turning off the lights. So “diurnal corals” get their food – but there is still enough food in the water for the corals, that open their polyps at night. Different areas of the tank are supplied separately – the outlet shaft in which is a large population of plankton gets its boost with Pepper Reef for some times, and aswell the refugium in the sump.
Smooth laminar flow is also important for the accommodation of the food, and the different requirements towards the flow rate needs to be considered. I switch on the feed mode at my Vortechs (about 10 minutes) and then turn to a changing flow. Overnight shutdown is also recommended.
Targeted feeding brings a lot of positive aspects. The color saturation of the corals increases, and they grow visibly faster and build up more compact branches. The individual branches are getting thicker the coral looks vital. A great polyp expansion appears when the corals get used to the regular feeding.
Amino acids promote especially the bold colors. It is critical not to overdose, otherwise the corals may darken.
The disadvantage that needs to be mentioned of the active feeding is that it affects all residents, including the hated aiptasia. These get the food as well. Animal helpers (filefish, various shrimp) should help to get a long with it. Aiptasia are solely in in my outlet shaft.
The feeding of corals is a good way to improve the colors and vitality of coral fundamentally. It only makes sense, if the water parameters and nutrient values are constant and a good and sufficient light and flow is available. Especially in tanks that are on zero nitrate and phosphate the active feeding is recommendable.
The indirect feeding by an increase of the natural zooplankton should also always be targeted – also due to the fact that we maintain a variety of fish, pick the whole day on the stones. With the products mentioned above, we could provide a constant stability in bold colors and vitality for about a year.
Kindly supported by: www.reefcare.de