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Presented by Charles & Linda Raabe
Mactan Island, The Philippines
© 2015 All Rights Reserved

  Corals, What one thinks of when the word "reef" is invoked, yet that same word tends to place all coral species in one big group that all require intensive lighting and strong water flow. Of course this is not true and leads to many coral deaths when little is known or understood of each species specific needs.
  A bad, yet understandable habit that we as hobbyists have is wanting to place "one of everything" or have a "nice mixture". This habit almost always leads to problems for many of the tank's inhabitants due to allopathy, improper lighting conditions, water flow, as well as compatibility issues. Most corals have very effective means to kill off their unwanted nearby neighbors.
  When planning a reef tank, I would like to suggest that you decide upon what type of species tank you wish to have and then stick with that plan. Mixing soft corals with stony corals, and various stony coral families can lead to long term problems, not only in coral aggression issues, but consider their lighting needs as well. Not all species of corals appreciate being put under metal halides.
  With having access to the internet, there are many available examples of reef aquariums that have done well over the long term with the species that are kept. By looking around, as well as reading a variety of online articles relating to these issues, it will give you a much more informed picture of what can be accomplished.
  While not always an easy task, when planning the placement of corals, try to imagine what their growth over time will require as far as spacing goes and which species or two will most likely become dominant in the system, this should allow you to plan your selections accordingly. There are few wild reefs that have ten different species located within a tank sized area due to just those reasons. Over the course of years, one species will become "the king of the hill". Expect the same to happen within your system.

Acanthastrea rotundoflora by Charles Raabe
(  Acanthastrea Rotundoflora )

A 2mb Home Movie of a Philippine Reef

   CORAL REEFS - What are they, where are they and what types there are.

   REEFS ON THE WEB - An exensive collection of very informative sites.


  RENAMING OUR CORALS - Lets get a little more specific please.

  REEF COLLECTING - For those of you who are able to do your own ocean collecting.

  THE NUTRIENT DYNAMICS OF CORAL REEFS   Part Two - A must read in my opinion.

  CORALPEDIA - CARIBBEAN SPECIES -  Not listed under the ID section since we can not keep these species, but a very good visual site.

   LIGHT, COLORS AND CORALS - What influences and creates coral coloration.

  CORAL FLUORESCENCE - How corals do it and why they do it.

  CORAL FUSION AND GRAFTING - Just when you thought it couldn't get any stranger.

  ZOOXANTHELLAE - This article discusses Clads "A" and "B".

  CORAL POLYP EXPANSION - Not a good indicator of coral health as many variables can dictate this behaviour.

  CORAL AGGRESSION - The mechanisms corals have to attack other corals. See Nematocysts also.

  Photo by Charles Raabe   Photo by Charles Raabe
                Sweeper tentacles

  CORAL FEEDING STRATEGIES  Part One of Seven  -  What foods corals utilize and how they utilize them.
                                              Part Two   Part Three   Part Four   Part Five   Part Six   Part Seven

  PHOTOSYNTHESIS AND THE REEF AQUARIUM - Carbon sources, Looks at photosynthesis in reef aquaria from a chemical perspective.

   Corals optical ability ?  -  " In many species of symbiotic corals, spawning occurs synchronously several nights after the full moon. This process is correlated with the level of lunar irradiance, but the mechanism by which these cnidarian/zooxanthellate symbioses can detect such low levels of light remains unknown. Here we report the first biophysical evidence that the host animal exhibits extraordinarily sensitive photoreception in the blue region of the spectrum. Using a high-resolution laser-induced signal to detect tentacle scattering, we measured the effect of low irradiance on the contraction of polyps in the corals that normally have their tentacles extended in darkness. Similar to most deep-sea invertebrates, the action spectra of coral photoreception reveal a maximum sensitivity in the blue, at 480 nm, with a spectral band width (at full-width half-maximum) of ca. 110 nm. The spectra closely overlap the maximal transparency of oligotrophic tropical waters, thus optimizing the perception of low light at depth. The detected threshold of photoreception sensitivity is ~1.2 x $10^{15}$ quanta $m^{-2}\,s^{-1}$ in the blue region. This makes corals capable of sensing the blue portion of lunar irradiance, as evidenced from the recorded slight contractions of polyp tentacles under variations in moonlight intensity."

  Most corals are Broadcast spawners releasing gametes once a year, sometimes twice a year. Such spawning events usualy occur over the coarse of a few nights. A small minority of corals are brooders, releasing their planulae monthly or every few months.

  SEXUAL REPRODUCTION - The release of eggs / sperm into the ocean's currents as shown in the above graph.

   Shown below is my Pavona sp. releasing sperm.
     Photo by Charles Raabe

  Common Asexual Reproductive methods:

 Longitudinal Division: This is where the coral divides into approximately equal halves, thirds, quarters, etc, like when a pizza is cut. Each piece has part of the oral (mouth) and basal (foot) disc then heals up and forms a new coral, typically moving away from the other corals.

 Budding: This is where the parent polyp will form a slight projection somewhere on its body and a new polyp will form at this point. The new polyp, called the daughter polyp, will either stay attached to the parent polyp or detach from the parent polyp and grow into a new coral.

 Pedal Laceration: This is where a portion of the basal disc will detach from the parent polyp. Then either the parent polyp moves away (most common) or the portion of the basal disc will move away. Eventually the fragment of the basal disc will grow into a new coral.

 Stolon Growth: A "runner" is sent out from the base of an existing polyp. As this runner (called a stolon) grows, it begins to form new polyps along its length. The stolon can be very thin, sometimes breaking in pieces, or it can develop into a thick mat, depending upon the species. This is seen most commonly in zoanthids.

 Transversal Division: This is where the coral will split along a horizontal line between the base of the coral and the top of the coral. The oral disc will be carried away by water currents and if it survives it will attach and grow a new foot. The basal disc will simply regrow a new oral disc and mouth. This is most commonly seen in Actinodiscus sp. mushrooms.

Fragmentation: This is where a portion of the coral is deliberately released by the parent colony (as opposed to a wave breaking a coral in nature or a careless hand breaking a coral apart in our tanks) and attaches in a new location to form a new coral. This is commonly seen in Capnella sp. or other similarly structured soft corals.

Self-Fertilization: This is when a male polyp releases sperm into the water and that sperm fertilizes an egg from a female polyp in the same coral colony.

  POLYP BALL FORMATION - First reported in a Goniopora species where the colony forms little miniature versions of itself, complete with skeletal mass and drops them. The photos below are of my Goniopora species doing the same.

     Photo by Charles Raabe   Photo by Charles Raabe

  THE PRESENCE OF GONADOROPIN-RELEASING HORMONES - The objectives of this study were to investigate the presence of immunoreactive GnRH (irGnRH) in scleractinian coral, Euphyllia ancora, study its seasonal variation, and evaluate its biological activity.

Modern captive coral reef aquaria ecosystems have attained the capability for supporting the long term healthy maintenance of many tropical reef corals. The stimulation of asexual reproduction has also occurred for many species and captive propagation is proceeding slowly. "

  For those interested, and you should be, in having corals reproduce within an aquarium setting, the best chance we have of being successful is by keeping those species that reproduce by planulae brooding, this is where the corals eggs are fertilized internaly, forming planulae (coral larvae) which are then released.
  This type of reproduction gives us the best chance at having corals reach settlement and form new colonies.  Below is a list of coral species that are known to be brooders as provided by Eric Borneman.

Photo by Charles Raabe  Photo by Charles Raabe
Photos taken on 6 Nov. 09 in my aquarium, with a count of 39 new coral recruits

  Agaricia agaricites, Agaricia fragilis, Agaricia humilis, Agaricia tenuifolia, Alveopora daedalea, Alveopora japonica, Astroides calycularis, Balanophyllia elegans, Balanophyllia europaea, Balanophyllia regia, Caryophyllia cyathus, Cladopsammia rolandi, Cyphastrea ocellina, Euphyllia glabrescens, Euphyllia rugosa = glabrescens?, Eusmilia fastigiata, Favia fragum, Favia gravida, Flabellum curvatum, Flabellum impensum, Flabellum thouarsii, Galaxea horrescens, Goniastrea aspera, Goniopora decima, Heliofungia actiniformis, Isophyllia sinuosa, Isopora brueggemanni, Isopora cuneata, Isopora palifera, Leptopsammia pruvoti, Letepsammia formosissima, Madracis formosa, Madracis mirabilis, Madracis myriaster, Madracis pharensis, Madracis senaria, Manicina areolata, Monomyces rubrum, Mycetophyllia ferox, Pocillopora damicornis, Porites astreoides, Porites furcata, Porites heronensis, Porites murrayensis, Porites panamensis, Porites porites, Porites sillimaniani, Porites stephensoni, Rhizopsammia minuta, Scolymia wellsii, Seriatopora caliendrum, Seriatopora hystrix, Siderastrea radians, Siderastrea stellata, Stylaraea punctata, Stylophora pistillata, Trochopsammia togata, Tubastrea aurea, Tubastrea coccinea, Tubastrea diaphana, Tubastrea faulkneri.

  Far to often I see forum threads started asking what species a certain coral is, while showing a photo or two (often blurry) of a coral within an aquarium. I understand that everyone would like to know what species they have, and it is important to know, if possible, what you have as it allows you to better understand how to care for a specific species.
  What is perplexing though is that few hobbyist seem to understand what is involved in determining species identifications. While there are a few, very few, corals that one can glance at and know its species (elegant corals as an example), The vast majority of corals will have to have a skeletal examination done in order to determine species. While a photo may allow you to narrow the coral down to a genus group or two, it will most likely never allow you to determine species.
  If you truly want to know, and be sure of a species identification, it will be up to you to either provide clear, in focus, macro photos of the corals skeletal features to allow others to identify your coral, or you will have to take the time and effort to learn how to do such examinations. The links provided below will get you off to a very good start.

These articles will present information required to properly identify many corals and what the obvious features tell us as reefkeepers. "

  A SIMPLIFIED GUIDE TO BASIC LEVEL IDENTIFICATION - Terminology, Basic identification features of corals.

  CORAL GENUS IDENTIFICATIONS - My own webpage listing pictorial stony coral genus groups.

  ACROPORA IDENTIFICATION KEY - A very usefull identification key for the acropora genus.

  GLOSSARY OF CORAL MORPHOLOGY - Terminology and identification featues used to identify species.

  CORALLITE ORDER & CYCLE EXAMPLES - A key to corallite identification features.

  Since it happens often enough, I think it is important enough to discuss. I have seen a great many online questions regarding the loss of Acropora species as well as having other corals slowly becoming unhealthy and eventualy dieing. A great many times, this can be attributed to an improperly stocked aquarium. In that, we all would like to see a nice mixture of coral species within our systems. Yet this same mixture will most always lead to trouble in being able to maintain the more sensative species such as the acroporas.
  Of course, elevated levels of nutrients and the overall quality of the water can play a large role as well. If you are trying to keep coralliamorphs, gorgonians, large polyped corals and others, such as hydnophora, galaxea or any of the "soft" corals. You are in effect, possibly creating a toxic soup within your aquarium through the release of such coral's chemicaly defesensive methods (allelopathy).
  If you see your Acropora species losing tissue fairly quickly, you might want to take a hard look at what species you are keeping together. If you wish to keep species such as the Acroporas and Montiporas, I suggest you keep only those species in your aquarium.

  THE USE OF PHYTOPLANKTON - I am sure like many of you, when I first started out, the store shoved a bottle of phytoplankton at me and said I would need it to feed my corals. Of course years later, I find out that corals do not actualy consume phytoplankton, they may inadvertantly capture it, but will soon reject it. This is not to say that you should not provide phytoplankton to your aquarium though.
  There are, or at least, there should be a good many other creatures in your aquarium that will benefit from the dosing of phytoplankton. Any number of copepods, worms, and a host of other very small animals feed on nothing but phytoplankton and other algae. By being well fed, they will in turn reproduce and in their swimming or crawling about, will feed your corals. Just as they do out on the reefs.

  FEEDING YOUR CORALS - I have two words on this subject, DO IT. It simply amazes me to hear others stating that they never feed their corals since corals get everything they need from the light. Granted, the light provides for the needs of the coral's zooxanthellae which in turn provides for the coral's energy needs. They do not however, provide for the corals protein needs. A requirement for growth, reproduction and healing.
  Such protein only comes from feeding. Without it, a coral must resort to direct nutrient uptake out of the water, and if the aquarium is being kept as nutrient free as possible, what does that leave the coral to eat if they are not being fed actual food? Besides, why would a coral polyp have a mouth and the tentacles / filaments to gather and eat food if they did not need them? Its just common sense that they require food, and a great deal more of it than you would think.
  If you have, or ever get to have the chance to dive on a coral reef at night, you would be amazed at how thick the water is with tiny swimming / drifting life forms, all of which the reef's corals actively capture and eat, each and every night. In addition to eating plankton, there is also a great deal of particulates (organic debris) available to the corals at all times of the day. In short, corals eat food, and they eat a lot of it. So please, feed your pets and stop starving them.

  HOW MUCH LIGHT - A perfect example of how corals do not all need high intensity lighting, in fact, for a good many coral species, such high intensity is actualy very harmfull to them. Please take the effort to study each species that you wish to keep.

  CORAL DISEASES AND PARASITES - Common coral problems with additional links provided.

  CORAL FEEDING ARTICLE -  What to feed, how to feed.

  DETRITUS - An excellent article which to me, is yet another good reason to not use particle trapping filters.

  FEEDING A CORAL REEF AQUARIUM  -  How and what to feed all of the inhabitants of a typical reef aquarium.

  REEF TANK FEEDING RECIPE -  Make your own reef foods.

  CORAL LIGHTING ACCLIMATION -  How to safely acclimate your new corals to your system.

  CORAL PHOTOACCLIMATION & PHOTOADAPTATION -  An indepth article on acclimating corals.

  THE LITTLE BRAIN THAT COULD -  An example of how to care for a damaged coral.

  LIGHTING -  Selection and Recommendation Links (also found within the equipment section).

  THE USE OF SUPPLEMENTS AND ADDITIVES -  My opinion on this subject.


  Coral Feeding : ( Quote Eric Borneman ) Corals need carbon, nitrogen, phosphorus and other trace and minor elements (these are largely unknown). The degree to which they get them depends on the sources - they can absorb from the water column, feed on particulates, use photosynthesis, use bacteria (directly and from their metabolic breakdown-products that they produce growing on the surface of the corals) and from prey capture. Most carbon is from photosynthesis and feeding. Most nitrogen is from feeding - if you have a lot of particulates and/or the corals has relatively low metabolic needs, it might be able to "extract" what it needs from the water. If not, then you should feed the corals. Chances are in tanks, prey is very limited compared to the wild. So, I think feeding is a good idea. Target feeding is fine, but use of water column particulate prey or psuedo prey like Artemia nauplii, Cyclop-eeze, oyster eggs, rotifers, etc is just fine provided there is a good amount in the water column for little polyps to feed. A half teaspoon a night in a 180 packed with corals, for instance, is pretty useless. Target feeding, for me, is a pain. I just load the water column so the tank water is awash in particles. I am pretty sure most every polyp gets several mouthfuls without going to the trouble of target feeding. If you have the patience and few enough corals to do this, great! Also, there is no "rule" on which corals need to be fed since they all feed - except for the handful of soft corals, Mycetophyllia, and Pachyseris which also feed, but in a different way."

  How I feed my corals and planktivore fish :  Since Linda and I eat a good deal of fresh fish bought from the local markets, usualy small mackeral species, I have found that at least one, usualy more, of the fish when being cleaned for dinner contains a good amount of roe. Having noticed how small the eggs are, it dawned on me that I have a year round ready supply of fresh food to feed my reef system with.  As such,  I simply collect the roe which are contained in an extremely thin, transparent sack that is easily broken by simply scraping the edge of a teaspoon across it.  Once completed, I simply mix the eggs into a large cup of tank water and refridgerate for ready use.

Photo by Charles Raabe   Photo by Charles Raabe


  First, I have to say that it is a crying shame that I feel the need to have such a catagory, but with the hobby continualy bombarded with hype, experimental methods, voodoo science and wishfull thinking, A few such topics need to be addressed.

  Dosing Sugar or Vodka  -  A great new method or aquarium russian roulette ?

  Supplementing Amino Acids  -  Another case of hype before the science.

  SECURING PROPOGATED CORALS -  Now that you cut your favorite coral in half, how do you secure it?

  CORAL FRAGMENTATION -  How to properly fragment a coral.

  PROPAGATION OF SMALL POLYPED STONY CORALS -  How to properly fragment small polypedcorals.

  CORAL CULTURE IN SUSPENSION -  A method for growing out coral fragments.


  GROWING CORALS FROM SEXUALY PRODUCED LARVAE -  A new approach to farming corals.

  THE FRAGGING PHENOMENON -  Another good coral fragging article.

  FRAGGING ZOANTHIDS -  A great article on how to do it safely, also a great zoanthid website.

Genus/Species Specific Information:

The above graph can be used to get a good idea on how dependent a given species is upon our target feeding of them.

Auto trophic = Light dependency for its primary food source.

Hetero trophic = Food particles / prey dependency for its primary food source.

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This mirror is being hosted with the permissions of the original content creator for preservation and educational purposes.