As I was perusing the coral tanks in a fish store a year or so ago, I recall overhearing a conversation between a staff member of the store and a budding reef hobbyist. A large display aquarium sat just around the corner replete with many stony corals, mostly of the genus Acropora.

"This," the staffer explained, "replicates a high energy reef zone. The lighting is strong, the water flow is strong and the corals are fast-growing." Well enough said, I thought to myself. "These are mostly small-polyped-that is, small-mouthed-corals." I suppose that's true, I thought. Those corals do all have fairly small polyps. "These corals, on the other hand," pointing to a tank containing colonies of the genus Euphyllia and then motioning to some mussids and a few Trachyphyllia, "are large-polyped-that is, large-mouthed-corals. With such a large mouth they tend to have a large demand for food and a smaller demand for light, whereas the small-mouthed corals tend to have a bigger demand for light and less demand for food." The hobbyist nodded excitedly as she was introduced to a new world of knowledge. I couldn't help but sigh to myself.

Having spoken with hobbyists from across the country and at many experience levels, it is my distinct impression that most people have no idea how dissimilar different species of coral are, and that they differ in some very important ways. This is very understandable, though. Most corals cannot be identified to the species level simply by looking at them. The conundrum we face as aquarists is that a large and diverse group of animals have numerous species that look more-or-less similar yet the needs of these animals, their tolerances and countless other variables important to their care are often very different. Understanding what differentiates the various species can be critical to their success in captivity. It is fortuitous for hobbyists, then, that most corals are very adaptable. Even if the perfect set of conditions is not achieved (as if anyone has any idea what is "perfect" for even a single coral species, much less all species), most corals will grow and live just fine. An ideal environment is rarely, if ever, available in nature, after all. Because of these tolerances, people were able to discover acceptable methods of maintaining certain corals over the years. Then, when similar looking species were imported, the same recipe for success was applied to them. Very quickly, the methodologies that proved successful for some species became "the way" to keep all species that had a "similar" physical appearance. After several years reefkeepers solidified a particular method of husbandry for each recognized group: small-polyped stony, large-polyped stony, and soft corals, zoanthids, and mushroom polyps. The problem with applying this cookbook style of reefkeeping is that it utterly ignores the true diversity that exists within or between each group. This is analogous to saying that seals, bears and wolves are really all the same animals and have the same needs. Obviously, this is not the case, yet a similar argument is propagated in reefkeeping circles simply by utilizing these terms and believing that they confer some knowledge about a certain coral's requirements. Simply put, the idea that these terms give us any useful information about light, water flow, food or any other requirements is a myth, and I wish to debunk it.

Stony corals can be found in very shallow water or intertidally regardless of the size of their polyps.
Photos courtesy of Eric Borneman.

The Myth

The biggest risk of simplifying is always oversimplifying. It is important to communicate without tossing in every detail and minutiae because, usually, too much is known about anything to say everything at once. Communication should be detailed enough to get the point across, and not much more. In trying to relay a great deal of information or necessarily complicated information, it is possible to leave out important details-details that make a big difference-merely in an attempt to make the message understandable. If someone said to a reefkeeper, "Tell me everything you know about having a reef tank in ten minutes," he or she would struggle to generate anything coherent at all. Probably what most people would do is start with very basic ideas: aquarium, live rock, saltwater, pumps, lights, skimmers, etc. Certainly, given time, most anyone could describe how to set up a new tank, or more-or-less how to replicate his or her own. Without a doubt, however, many finer points that wouldn't be mentioned in this first meeting are required knowledge when keeping a tank. For example, someone might forget to mention to use freshwater and not saltwater for evaporative top-off. Most new hobbyists would never think to use anything but saltwater for top-off in their saltwater tank, and as is obvious to an experienced hobbyist, up would go their salinity. Weeks or months later, as the salinity has risen near 50 psu and everything in the tank is dead or dying, the new hobbyist will wonder why and have no idea what to do. Of course, all that was needed was freshwater top-off, or rather the information that freshwater top-off is required. This is a minor detail, and something most people wouldn't think to mention and most new hobbyists wouldn't think to ask about, but nonetheless it is critical to the tank's success. I would suggest that using terms such as SPS, LPS or any other such shorthand is very much like saying, "Use saltwater in your saltwater tank," with no other information. It is a gross oversimplification of very large and complex groups, and to base decisions about care, hardiness, aggression or any aspect of husbandry at all on these designations can, and will, lead to problems and mortality, not to mention thousands of wasted dollars and heartache on the part of the aquarist. As I will explain in the following sections, it simply is not good enough to say something is an SPS coral and therefore should receive the care that other SPS corals need, or that something is a softy and is therefore tolerant of some set of conditions like other soft corals.

First, let me review each of the five recipes-the five myths-before I go about re-evaluating them. This isn't likely new information for anyone. Indeed, this is what people already know, or rather, what they think they know. Through my experiences and contact with other aquarists, I believe these five characterizations are representative sentiments of the majority of hobbyists with regard to each group.

  • Mushroom Polyps (order Corallimorpharia): They like dirty water with high nutrient levels. They don't like bright light or much water flow. They don't need food, just some light and nutrient-rich water. They're very hardy and are great inhabitants for a new tank.

  • Zoanthids (order Zoanthidea): They should be called zoos because they are ZOOanthids. They don't care about dirty water with high nutrient levels. They don't need much light or water flow. They don't eat; they just use light. They're very hardy and ok to put into a new tank.

  • Soft Corals (subclass Octocorallia): They need dirty, nutrient-rich water. They don't like bright light or strong water flow. They produce toxins that hurt "SPS." They don't need food, just light and nutrients in the water. They're good to put into a new tank, and to later upgrade to stony corals. They're very hardy.

  • LPS Corals (order Scleractinia): This is an acronym for large-polyped stony/scleractinians, i.e., stony corals with relatively larger, fleshier polyps than SPS. They don't mind nutrient-rich water. They don't like very bright light or strong water flow. They need to be fed on occasion. They're hardy and good to mix in a tank with the previous three groups.

  • SPS Corals (order Scleractinia): This is an acronym for small-polyped stony/scleractinian corals, i.e., stony corals with relatively smaller, less fleshy polyps than LPS. They need very clean, nutrient-poor water. They need super-bright light and very strong, chaotic water flow. They don't need any food, just light. They're very sensitive and difficult to keep. They don't take stress well. When they're happy, they turn beautiful colors, but only if the tank is nutrient-poor. If they aren't colorful, nutrients in the aquarium are making them turn brown.

The Reality

Most people probably have sentiments in keeping with the bullets above, though I've listed these ideas as myths. It is said that there is some truth to every myth, and that is very much the case with what I've stated above. The problem is, again, an oversimplification that leads to ideas and methods that are just downright incorrect or harmful. To illustrate why these ideas don't hold up, I'll take each section above and point out its half-truths and incorrect information.

Mushroom Polyps (order Corallimorpharia)

Mushroom polyps, which are termed corallimorpharians, are often said to "like" or "need" dirty water in order to do well. Well, let's see why. I've certainly seen tanks that had very high nitrate readings along with detectable phosphate that grew mushrooms very well. These tanks usually have a very small, or no, protein skimmer installed. Some mushrooms certainly seem able to tolerate high nutrient levels. I've also seen other tanks with very low levels of nitrate and phosphate due to the use of a large skimmer and minimal feedings. Sure enough, the mushrooms didn't grow well at all. So, case closed, right? Mushrooms + nitrate = good, right? Well, it's not that simple. Various species of corallimorphs grow in a variety of environments in nature, but the species we are all interested in, and the ones that we put into our reef tanks, come from tropical coral reefs. Most species are found in somewhat protected parts of the reef, often in turbid water. Nowhere on a coral reef, however, do the nitrate levels approach even a twentieth of what is often considered high or nutrient-rich in captivity. They grow just fine on the reef even though the dissolved nutrient levels (especially dissolved inorganic nitrogen, DIN) are extremely low (see D'Elia and Wiebe, 1990). Hmmm, perhaps it's not that they need dirty, nutrient-rich water. One thing that is present on coral reefs in great abundance (Anthony, 1999) that is usually much scarcer in reef tanks is particulate organic material (POM). This is the term for feces, algae, bacteria, mucus and other gunk floating around in the water. Often tanks with small protein skimmers contain more of this material (as well as dissolved organic material, DOM-the division between the two at the lower size ranges is somewhat arbitrary) simply because the waste produced in the tank is not readily removed, so it can become suspended. In tanks with big skimmers, most of this material is quickly removed. Corals seem to actively use this as a food source, and those living in calm areas rely on it more heavily (Anthony, 1999; Anthony and Fabricius, 2000; Mills et al., 2004; Mills and Sebens, 2004), and mushrooms are no exception. Perhaps what they like and need is not nutrient-rich water but rather food in the form of suspended or dissolved material. I would suggest that this is exactly the case. The largest species of corallimorph, Amplexidiscus fenestrafer, is in fact a piscivore and may actively lure fish to itself with chemical attractants (Hamner and Dunn, 1980). Many other species, especially azooxanthellate corallimorphs, can be very active predators. There are a few little Pseudocorynactis sp. in one of my tanks that feast on any particle they can grab whenever I feed the aquarium. In fact, recent studies confirm that corallimorphs thrive on portions of a reef with a high availability of particulate material (due primarily to land-based run-off) and can even competitively displace stony corals in such situations (Kuguru et al., 2004; Muhando et al., 2002).

The problem with generalizing about their need for light is that there are many species in this order and each has different tolerances and requirements. Many aposymbiotic (lacking zooxanthellae) corallimorpharians can be found growing in very dim locations, either in deep water or in shaded locations, but not always. Other species grow in turbid water, on vertical walls, in overhangs or in somewhat shaded locations. Still other species (or other individuals of the previous species) grow in clearer, shallower water and receive much more light. Ricordea florida is regularly found in seagrass beds, often in only a few feet of water, but it also lives in deeper water and can be found in much dimmer light. On a recent trip to the Caribbean I found a large Discosoma sanctithomae (which may be reclassified as Rhodactis sanctithomae soon) colony growing in about 3 m of water on the north side of St. John, USVI. The colony was oriented at an angle (which diminishes the amount of light received by the coral), but the sun here was still intense and not at all reminiscent of what is often recommended for these corals. The problem is that different species and different individuals can, and do, live in radically dissimilar light levels in nature. Interestingly, Muhando et al. (2002) found the corallimorphs in their study to be most common in the shallowest water, especially on the reef flat and reef crest where conditions (such as aerial exposure during low tide) may be stressful. We would all be foolish to think that this large group of organisms has a single and particular light requirement. The same can be said for water flow requirements. None of the species we keep in aquaria seems to prefer truly strong water flow, but some are obviously more adept at utilizing it than others are. The Discosoma sanctithomae mentioned above was found growing not more than a meter away from a large Acropora palmata (a coral dependent upon strong water flow) and in a fully exposed position. The wave action here is normally quite strong, though it was relatively calm the day I visited. Other species such as the lovely, temperate Corynactis californica typify areas of strong currents and crashing waves. Were this and similarly adapted species kept in weak water flow it could be disastrous for them. Species with many surface irregularities such as Ricordea spp. and Rhodactis spp. are often found in areas with significantly faster water flow than those with smooth surfaces, but not always. This, too, is a simplification and we cannot say with any degree of certainty (at least at this point) that a coral came from a particular location because it has some particular polyp shape. Realistically, the best that can be done at this point is to observe the coral in the aquarium and see how it responds to various flow regimes. Creating rules and recipes to apply to corals can always falter. Observing how a particular coral responds to particular stimuli (more or less water flow) cannot.

As for the last point, many corallimorphs are very hardy, but not in every situation or in every tank, from what I have seen. Usually these corals seem to thrive in most reef tanks and reproduce spontaneously. I have seen on many occasions, however, these same corals languishing, shrinking and eventually dying in other tanks, especially those that are more than a year old and that are considered to be very nutrient-poor (usually meaning small food additions and significant nutrient removal) by reefkeeper standards. Why they might thrive in one tank that seems to be in poor condition only to die in another seemingly healthy tank is the subject of another debate, but nonetheless they are not the easy, "can't-kill-them," "everybody-can-keep-them" corals that they are often said to be. They, like any organism, can do poorly in captivity, and especially in new tanks they can have a hard time just as other corals can. They have certain requirements for health and vigor. If these are met, they thrive; if not, they don't.

Zoanthids (order Zoanthidea)

Notice that this word contains only a single "o." A zoo is a place where animals are kept on display, whereas zo-(rhymes with toe) is a prefix meaning "animal." Actually, the prefix zo- and the word zoo have completely different etymologies; that they appear to be similar is just coincidence. This is a simple point, but I can't overstate how it grates on the ears of folks who know better. My advice in any endeavor would be to know the correct pronunciations of its words; otherwise we seem less-informed than we truly are.

As mentioned above for corallimorpharians, zoanthids do not need and are not necessarily healthier in high nutrient water. Tropical species often grow on the same reefs as our other corals, and there is no reason to assume that their needs for dissolved inorganic nutrients should be different than that of any other groups of corals. They do seem fairly tolerant of conditions that other corals often don't tolerate, but this is no reason to push them to their limits. They have no more place in a new, immature tank than does any other coral. Similarly, a dog might be able to go two months without food whereas a cat might only survive one month, but who would test this on their pets? It probably isn't a good idea to see how far our charges can stray from suitable conditions and still survive. Along these lines, nutrient-rich water does not satisfy all the nutritional needs of most zoanthids. In fact, many of them are decidedly predatory (Tanner, 2002) and some absolutely feast on any food offered. Other species tend to be much pickier in what they will accept. In general, species in the genus Zoanthus tend to rely heavily on light, dissolved nutrients and detritus. Some species readily take certain prey but reject many others. Finding out what they will and won't take is largely a matter of trial and error. In nature plenty of whatever they eat is usually available, so obtaining sufficient food is rarely an issue for wild zoanthids. Due to the very limited plankton populations in our tanks, this is not the case in captivity. Species from some of the other genera tend to take food more readily, especially some Protopalythoa spp. Some individuals in this genus can be absolutely ravenous, and while they use light to a large extent (like most reef corals), food seems to be more important (Tanner, 2002). The polyps of a particular colony that was in my care often would catch and engulf five or six pellets or two or three mysid shrimp at a time. Each polyp would then reopen within minutes and take the same amount of food again. I have fed this colony this amount of food four and five times a day, and it eagerly takes the food each time and expands again, tentacles waving in the current. So much for zoanthids not eating.

In terms of light intensity and water flow, luckily, these corals are very adaptable. They certainly can and do grow in modest light levels and weak water flow, and this is often what they're given in captivity. More often in nature they are actually found in shallow water where light is very strong and water flow can be turbulent. On a large granite boulder in "The Baths" on Virgin Gorda, BVI I saw a carpet of Palythoa sp. covering at least 300 if not 400 ft.2 reaching from the surface to about 2 m depth and exposed to crashing waves without any shade from the sun whatsoever. While the majority of species can be found in shallow areas, some are found almost exclusively in deeper water. Again, variation is the rule and classifying any sort of conditions as the "right" conditions for this group ignores the fact that each colony can be very different from every other colony. No two species are the same and there are likely many species (though they need taxonomic revision).

Soft Corals

The sentiments in this hobby regarding the needs of soft corals have really troubled me for years. Unfortunately, many folks have a very inaccurate image of how and where most soft corals live in nature. A lot of people would be shocked to learn that many of the soft corals we keep in our tanks normally grow right alongside the so-called high-light, high-flow stony corals that many of us strive to maintain. While some coral reef soft corals certainly grow and survive best in lower light levels or very calm water flow, the majority do not.

When most people think of the preferred habitat of many common soft corals such as those in the genera Sarcophyton, Lobophytum and Sinularia, they all seem to come to the conclusion that it is an area of low light and low water flow with high levels of dissolved nutrients. Perhaps these species live just in deep water and in turbid lagoons where they might have access to these conditions. While some of these species can be found in those areas, so can many Acropora that are adapted to shallow water, and I doubt that anyone would argue the preferred habitat for most light-loving Acropora spp. is a turbid lagoon. As discussed for mushroom polyps and zoanthids, simply no areas on a normal coral reef come anywhere close to what hobbyists consider nutrient-rich or have high levels of nitrate and phosphate. Some soft corals may tolerate an elevated level of dissolved nutrients, but it is not something they need or necessarily benefit from, and it is no more natural for them to be found in this water than it is for the most sensitive of stony corals. Allowing the nitrate and phosphate levels to become elevated in an aquarium probably will not benefit these corals more than any other coral. Xeniids and some nephthiids are especially common in the ultra-clear waters of the Red Sea or on reef flats where water clarity is often quite high. These species may be intolerant of more stagnant areas.

Many soft corals grow in the extremely clear, nutrient-poor waters on outer reefs. They gain a great deal of energy from their symbionts due to the high water clarity, but also feast on very fine particulate material washed over the reef. Photos courtesy of Eric Borneman.

Many of the octocorals we keep are actually abundant in forereef, reef flat and backreef environments. While it's true that it is not unusual to find these species in deep water where light and water flow can both be quite moderate (though water flow is sometimes very strong even at those depths), they are very common in much shallower water as well. It is not unusual to see many commonly kept octocorals growing in mere feet of water exposed to more intense light than we would normally ever keep over our aquariums and more surge than we can easily duplicate. In fact, it is not at all uncommon to see these species growing intertidally such that they are exposed to the air for hours at a time at least several times per month. That soft corals as a group tolerate lower light levels is not a mostly true rule with exceptions, it is a rule that applies only to the exceptions! In fact, contrary to popular belief, many octocorals are able to not only withstand but actually benefit from brighter light than many stony corals, including Acropora spp. (photosynthetic saturation is often found to occur at higher irradiance levels in some octocorals than most scleractinians). In terms of water flow, these environments are often very well flushed and experience some amount of wave action and surge. Indeed, it is not at all uncommon to see thickets of Porites and Acropora interspersed with large monotypic stands of soft corals. Corals such as many Acropora spp. and many soft corals often are thought by aquarists to be a world apart in terms of their water flow requirements, yet they are found right next to each other on the reef. There is no reef environment where soft corals tend to be completely absent, and this includes many upper reef slopes and reef crests. What is apparent on most coral reefs is that stony corals tend to be more abundant than soft corals, though this is not universally true. For example, some reefs such as some in the southern Red Sea can be spatially dominated by octocorals. The reefs off of eastern Africa boast immense soft coral species diversity and are dominated by them. On most reefs, though, soft corals tend to grow as single colonies surrounded by hermatypic stony corals or as patches (sometimes monospecific, sometimes including several species). Soft corals also are able to utilize environments that are somewhat marginal for stony coral growth. More than anything it must be noted that soft and stony corals can and do grow in the same environments and that competition and perhaps the founder effect (whoever got there first) are key ingredients (along with species specific tolerances) in determining which species are present at specific sites. Soft corals grow where they can outcompete stony corals (and other organisms) for space.

Having said that, many soft corals do need very different conditions from those provided on a reef flat. For example, the gorgonian Diodogorgia nodulifera is typically found in deeper water (below 30 m especially) where the light levels are low and the water current is moderate. Many other such soft corals, especially aposymbiotic species are found in deep water. These species have proven categorically very difficult or impossible to maintain in captivity, however, and should therefore be avoided. Some soft coral genera such as Sarcophyton or Sinularia may be very hardy and adaptable, while others are quite the opposite. Still other species of aposymbiotic soft corals such as Dendronephthya spp. are found in habitats with their preferred water flow (strong and laminar) regardless of light levels. The light might be very dim or very bright, but the corals go where the food is and where the water flow can deliver it (Fabricius et al., 1995). These are also corals we cannot hope to properly husband with the current state of aquarium technology (see Delbeek, 2002). Soft corals are often regarded as easy to keep, yet many of the most beautiful octocorals are literally impossible to maintain in captivity. Decisions about care also cannot be made simply on a character such as growth form. The gorgonian genus Gorgonia typically produces large fans that can be several meters across. So does the genus Iciligorgia. While Gorgonia is zooxanthellate, Iciligorgia is azooxanthellate. While Gorgonia typically lives in shallow water, Iciligorgia lives in deep water. While Gorgonia grows best in areas of significant surge with clear waters, Iciligorgia typically lives where water flow is more moderate and laminar and the water is turbid. While the two look quite similar, they are not, and these differences must be recognized if success is to be had with either.

The degree to which soft corals use heterotrophy (feeding) to satisfy their needs can vary radically between different species. All of the aposymbiotic species get 100% of their nutrition through feeding. Other species such as members of the genus Xenia are more nearly autotrophic in obtaining their energy. These octocorals tend not to capture prey and instead increasingly use the photosynthesis of their symbionts and dissolved organics to meet their needs. All other species fall somewhere in between with some being more highly autotrophic (such as Anthelia) while others are more highly heterotrophic (such as Capnella or Nephthya). Variation is the rule, with each genus and species being different from the last. Given that there are hundreds of species of octocorals, that is a lot of variation and it is totally inappropriate to say that all soft corals have certain or particular feeding requirements. It must be stressed, though, that most soft corals are dependent upon heterotrophy for a significant portion of their nutrition (including their energy demands), especially at the moderate light levels they often receive in captivity (Fabricius and Klumpp, 1995). Further, soft corals can be very effective at utilizing POM, primarily when it is very fine (Fabricius and Dommisse, 2000).

These commonly kept soft corals are growing in very shallow water and therefore extremely bright light. It would take powerful metal halides to replicate this intense lighting. Left is a Clavularia sp., right is a Lobophytum sp. Photos courtesy of Eric Borneman.

Another concern when keeping soft corals is that they produce secondary metabolites, often in copious amounts. Secondary metabolites are usually low-weight molecules with complex and often unique structures. Some of these chemicals are, in effect, poisons. Soft corals in particular are known to produce a large variety of extremely toxic secondary metabolites (as are many other corals, though research until recent years has focused primarily on octocorals and zoanthids). In a recent search of the "Web of Science" using the keyword "Sarcophyton" I found that perhaps 80% of the hundreds of studies that arose discussed one or more of the metabolites produced by this genus. This is an area of a lot of research, mostly in the pharmacological field. While many corals, such as most zoanthids, store these compounds to decrease predation, some soft corals are known to actively secrete these substances into the water column in order to harm nearby corals, sponges and algae. Many people have assumed correctly that these compounds can be harmful to stony corals. What I find interesting, and sad perhaps, is that people have seemed to carry this idea only to "SPS" corals. People rarely keep soft corals (especially Sarcophyton, Sinularia, Lobophytum and other highly toxic genera) with so-called "SPS" corals, or are at least aware of this risk, but they rarely, if ever, consider the risks to other organisms. The toxins these soft corals produce may not be targeted toward Acropora in particular; rather, most of them are wide-ranging in their effects and are potentially harmful to any sort of stony coral, other soft corals, anemones, fish and even the aquarist! These effects tend to vary highly depending on the tolerance of the poisoned animal and many other conditions. The critical thing to understand is that they are potentially toxic to anything in the aquarium, but that some organisms are much more sensitive than others.

For this reason, the typical stocking protocol of most reef tanks couldn't be more ill-advised, in my opinion. Normally, reef aquarists stock tanks in order of the corals' perceived hardiness. Usually, "leather corals" (alcyonians), zoanthids and mushroom polyps are the first corals in the tank. They are usually tolerant enough to survive the poor conditions of a new tank, although even these corals often show problems. After a few months of these corals struggling along, the tank begins to mature and they start to do really well and thrive. As they grow the aquarist becomes confident that the tank is becoming healthy and starts to add "LPS" corals. The resident soft corals sense the intruders (chemoreception is acute in anthozoans) and begin to secrete more secondary metabolites, trying to prevent their intrusion. Some stony corals may tolerate being housed with these soft corals and do well, while others may not tolerate them and die. These become just a few of many mysterious deaths that the tank is likely to sustain. As more time goes by and the resident corals grow and fill more space, the aquarist becomes more confident in his or her skills and begins to add all sorts of "SPS" fragments, often placed very near other corals including soft corals. Sure enough, the soft corals sense the intruders again (all corals, including stony corals, release chemical compounds into the water and corals use these to identify their neighbors). All the resident corals then begin an all-out assault on the newcomers, trying their best to keep new corals from settling so that they can retain their own space. Not only this, many of the corals are probably fairly large by this point and can make large amounts of allelochemicals. After a number of mysterious deaths the aquarist gets frustrated and either declares that stony corals are too difficult to keep or seeks help and perhaps starts using activated carbon and water changes to control the concentrations of secondary metabolites. Usually, some soft corals are removed at this point. After a few years the tank is once again stable, many stony corals are growing well, and there are fewer mysterious deaths than before. To reach this point, however, required the sacrifice of a number of corals that needn't have died. Instead of stocking first with competitive soft corals (and zoanthids and mushroom polyps) and then adding stony corals that are likely to be killed by the resident corals, it would be a much better idea to allow the tank to mature an extra couple of months without corals, then add hardy, pioneer stony corals to avoid these problems from the beginning. After a year hundreds of dollars will have been saved; few, if any, corals will have been lost; the resident stony corals will be growing large and beautiful and the only sacrifice will have been waiting a few more weeks to add corals. Impatience kills, every time.

Left: Notice the Acropora and other stony corals in the background while the Klyxum has completely overtaken an area of reef. Right: When they occur, soft corals often competetively exclude stony corals. Photos courtesy of Eric Borneman.

LPS Corals (order Scleractinia)

The three groups discussed up to now are real taxonomic units recognized by scientists (mushroom polyps comprise the order Corallimorpharia, zoanthids the order Zoanthidae, and soft corals the subclass Octocorallia). All species of stony corals comprise the order Scleractinia. What, then, is the taxonomic unit used to differentiate large-polyped from small-polyped stony corals? I'm asked this question quite frequently, and the answer is that there isn't one. The dividing line between what constitutes a "large" versus a "small" coral polyp is entirely arbitrary and based only on opinion. I hear from some aquarists that Favia is a large-polyped genus and from others that it is a small-polyped genus. I've heard the same about Turbinaria reniformis. There is no ecological or biological reason to divide stony corals based on polyp size. In fact, there is no natural divide at all-stony coral polyps can range from as little as 1 mm to over 30 cm across and different species embody this entire range of polyp sizes. The reality is that nearly every taxonomic family of zooxanthellate stony coral (there are almost 20) comprises species having very small polyps and very large polyps. Similarities in appearance do not necessarily imply similarities in relatedness (fortuitous for folks with balding, fattening relatives). Polyp size alone simply does not reveal the sort of care a stony coral should receive.

Top left: Compare the environment this Euphyllia ancora is growing in to the Symphyllia below. Both corals have large polyps, but they live in totally different environments. Top right: A Pachyseris sp. growing in the same reef as the E. ancora. Again, polyp size does not determine environmental needs. Bottom left: A large Symphyllia sp. growing in very shallow water. Bottom right: A small Symphyllia sp. growing just below the tidal line. Photos courtesy of Eric Borneman.

Some species aquarists ascribe to this group seem to tolerate elevated dissolved nutrient levels well, but this is extremely variable. While some are extremely tolerant in this regard, others can be much, much more finicky. This varies along species lines as well as occasionally between individuals. I've seen aquariums where corals such as Trachyphyllia geoffroyi were able to maintain themselves and appear quite healthy even as nitrate levels approached or exceeded 40 ppm. Some other corals normally thought to belong to this group, such as Euphyllia spp., seem far less tolerant in my experience. For example, a particular Euphyllia paradivisa in a friend's tank would begin to look quite badly whenever the nitrate was allowed to reach or exceed 10 ppm. The tolerances of the various species put in this group can differ radically. Something that won't bother one will kill another and vice versa. This isn't surprising as "LPS" is an artificial and arbitrary grouping of totally unrelated species. Humans (genetically, temporally and evolutionarily) are much closer relatives of whales and armadillos than some of these corals are to each other, and I am not exaggerating. Going back to the previous section, some stony corals are particularly sensitive to the presence of certain soft corals. Euphyllia (often placed by aquarists into a tank with soft corals) is regularly highly sensitive to them. In one particularly vivid example of their intolerance for many soft corals, I witnessed the effects of mixing a shipment of about 10 yellow Sarcophyton sp. with a tank full of various Euphyllia spp. There were perhaps 15 Euphyllia colonies, mostly E. paraancora, split between two 50-gallon tanks. The Sarcophyton were placed into each tank. Within three days all of the Euphyllia spp. looked terrible and within five days four colonies had been completely lost and many others were badly deteriorated. When moved to a different system, however, each colony recovered within a week. Merely a day after the move each colony had expanded a great deal, whereas they had been completely retracted before. Despite experiences such as this, aquarists insist on housing these corals with aggressive soft corals without forming a contingency plan in case the corals do not tolerate each other. I'm not sure why, except perhaps that the idea that larger-polyped stony and soft corals need the same conditions is so ingrained. While Euphyllia and some other genera seem very sensitive to being housed with soft corals, others appear to be very tolerant. I've never seen corals such as Mycedium be particularly affected by soft corals in the aquariums I've observed, but this is not to say they never could be. In fact, I bet soft corals somewhere on some reef or in someone's tank have affected them. Again, the point is that the variation is huge and grouping everything under a particular heading will cause problems and mortalities.

In terms of their water flow and lighting requirements, corals lumped into this group couldn't be more different. No species with large, fleshy polyps is able to tolerate most pounding wave action, but many are found in strong currents in nature, stronger than what most people provide even in "high-flow" aquariums. Corals such as many Lobophyllia, Favia and other faviids, Turbinaria, certain Goniopora, etc. all have large to very large polyps, yet are often found in quite strong water flow in nature. These species are common on reef flats and upper reef slopes where many of the light and flow loving "SPS" corals grow. On the opposite end of the spectrum, corals such as many Euphyllia, Trachyphyllia, other Goniopora, etc. are often found in deep or turbid water where light levels can be very low and water currents are often gentle (see Borneman, 2002). Those two environments are as different as night and day, yet aquarists say that all these corals belong to the same group and require the same conditions due to similarities in their external appearance. This simply is not so. The genus Turbinaria is an interesting case, in particular. This is a modestly-sized genus containing 11 species. Of these 11, two have large polyps, five have moderately-sized polyps and four have rather small polyps. Are we to believe that T. reniformis is more similar to Acropora, Montipora or Stylophora than to T. peltata because its polyps are closer to those in size? This is analogous to saying that I am more closely- related to someone I meet on the street who is my height than I am to my mother, who is shorter than I. If a doctor asks for my family medical history, whose should I give, my mother's or the stranger's? These species are found in essentially the same environments, too. Often they are found in shallow, brightly-lit areas with turbulence, though they are sometimes found deeper. Polyp size has nothing to do with which stony corals are related to which other stony corals or with their tolerances or requirements.

In terms of feeding, it has been suggested, both in aquarium literature and within the scientific community (Porter, 1976), that larger-polyped corals eat more than smaller-polyped corals. This hypothesis has subsequently been tested and has been shown to be completely baseless. Some corals eat a lot and some corals don't eat nearly as much, but polyp size rarely, if ever, has any correlation to this. If anything, larger-polyped corals are often found to eat less, not more, than smaller-polyped corals (e.g., Coles 1969; Sebens et al., 1996). What people generally have found is that some larger-polyped corals often cannot use light instead of food for as large a portion of their energy needs as others can. Some corals can get as much as 90% or more of the energy they need (not nitrogen or other nutrients, though, just energy) strictly from light (Bythell, 1988), whereas many larger-polyped corals are typically limited to less than 90%. In effect, all this means is that some larger-polyped corals are not as adaptable as others to differing amounts of food or light. If lots of light but no food is available, some corals with larger polyps cannot get enough energy and begin to starve in a short time. If lots of light but no food is available, some smaller-polyped corals can use the light more effectively and can stave off starvation for a little longer. Again, this is all speaking very generally, because each species and each genus is very different from the rest.

Though the tentacle development on these larger-polyped corals (middle & right) looks more impressive than the smaller-polyped coral to most people, plankters may have more to fear from the Seriatopora (left). Photos by Chris Jury.

SPS Corals (order Scleractinia)

I love the aquarists who consider themselves SPS aficionados (some of my best reefer-buddies are "SPS junkies"), but I really loathe this term. It is often used, yet it means absolutely nothing about a coral except that it can't eat really large pieces of food. Whoopee! The problem is that, as with each of the groups discussed here, aquarists think that this designation prescribes some particular sort of care or conditions, and this is nonsense. Most corals on a reef are stony corals and most of them have small polyps. Looking at various photos of a reef, "small-polyped stony" becomes nearly synonymous with "coral." The corals on a reef are almost all small-polyped stony corals. Some small-polyped corals are on the reef crest getting pounded by waves and light, and other small-polyped corals are growing two feet into a cave getting no direct light and little water movement. There are small-polyped corals that grow hundreds of feet down and have special mechanisms to capture the nearly invisible light. There are small-polyped corals that grow in fields of seaweed. There are small-polyped corals that live in places where the temperature fluctuates by 15° Fahrenheit in less than 10 minutes or varies from the 60's in winter to the low 90's in summer. There are small-polyped corals that survive, grow and don't bleach in temperatures that approach 100° F. in the summertime. There are small-polyped corals that live on mud flats in water so murky the visibility is not more than a few feet. There are small-polyped corals that are nothing like what people think they are supposed to be, and I tend to believe the corals are more right than we are.

Many soft and stony corals, including Acropora spp., grow near each other on reefs and in the same environmental conditions. Replicating this in the reef aquarium can be difficult due to the ability of many corals to compete aggressively. Don't try this at home (or at least keep a watchful eye)! Photos courtesy of Eric Borneman.

The first myth (which is really a half-truth) is that corals with small polyps strictly need very clean, nutrient-poor water. The reason this is a myth is that it assumes these corals are somehow different from any others. No coral needs or benefits from being kept in water with high amounts of nitrate or phosphate. Some tolerate it better than others, but no coral needs it. Some genera are particularly sensitive to these poor conditions, while others are more tolerant. Other sorts of stress elicit other responses. I've seen a Siderastrea that was overturned in a tank without light and literally partially buried in sand for a month perk up and start looking good again after only a week when turned back over. How many corals can do that? No matter what the stress is, some take it well and some take it poorly. "Small-polyped stony" describes a huge group of corals comprising hundreds of species and well over a dozen families, some of which have had independent evolutionary tracks for hundreds of millions of years. The genus Acropora alone comprises nearly 350 species, some of which grow in clear oceanic water on the tops of reef crests while others grow in muddy lagoons with dim light, slow water flow and a constant rain of semi-organic particles. It is easy to see why corals with small polyps vary so much in their stress tolerances.

Many Acropora spp. are adapated to live in lagoons. This environment is very different than what is often recommended for them. Photos courtesy of Eric Borneman.

As far as these corals' "strong light and water flow" requirements, this section's first paragraph should give us some idea of why no single recipe for success is enough. Some species are wide-ranging and can be found in many types of habitat-literally from upper reef slopes, to intertidal reef flats, to seagrass beds, to mud flats. Other species are more restricted and grow only in one particular habitat. For instance, Pocillopora molokensis is endemic to the Hawaiian Islands and is found only in deep water. Acropora hyacinthus is normally found in shallow water, but only where there are strong currents and flushing. The water flow can't be too strong, though, or its tabular growth form will allow it to be ripped off the reef. This species often grows on reef crests if they are not too turbulent or overly prone to storm damage. In the most wave-swept areas or those prone to storms, digitate Acropora and encrusting corals tend to be the only species that can cope with the harsh conditions. Other species of Acropora, such as many of the staghorn or bushy species, cannot grow here as the wave action or storms would too frequently break them apart (though there is a happy medium with some amount of breakage and fragmentation allowing for increased asexual recruitment and hastening spatial dominance of many species) (Highsmith, 1982; Riegl, 2001). In fact, most of the species that hobbyists often assume live on reef crests do not, in fact live there, including most Acropora, Montipora, Porites, etc. It is odd that aquarists often think their aquariums replicate a reef crest. I've never seen an aquarium that had sufficient water flow to shatter staghorn Acropora colonies, but perhaps there's someone out there who has the turbine from a jet engine attached to their tank. Polyp size simply has nothing to do with either light or water flow requirements. In fact, some smaller-polyped corals are among the most tolerant of variable light and current. Stylophora pistillata can grow in inches of water on the reef crest or over 30 m deep in almost no current, but this doesn't match the present view of what this coral is supposed to be. Again, I tend to trust the coral more than popular opinion.

Left: Klyxum sp. growing intertidally. Right: Heliopora coerulea, a very unique octocoral growing intertidally.
Photos courtesy of Eric Borneman.

As far as food goes, corals with small polyps eat, and there is no question about that. To reach the conclusion that feeding these corals is not important requires a reversion to the time before C.M. Yonge's studies in the 1930's on the Great Barrier Reef (or earlier), as well as complete ignorance of the past 75 years' worth of research. While it is true that some of these corals eat more than others, the species that are least reliant on food are not those that hobbyists believe are. In particular, study after study after study has found that corals such as Acropora are highly efficient predators, and that they eat large amounts of prey including a lot of zooplankton and particulate material every night in nature (Anthony, 1999; Anthony, 2000; Bongiorni et al., 2003; Bythell, 1988). Corals such as Porites cylindrica tend not to eat quite as much food as most corals, but they are the exception and not the rule (Anthony and Fabricius, 2000). They have merely circumvented the need for large amounts of food and can subsist on very little. Just to put some numbers on things, as aquarists tend to resist tooth and nail the idea that these corals eat things and need to be fed, Bythell (1988) found that Acropora palmata (the ultimate "SPS" coral) gets 70% of the nitrogen it needs for health, growth and reproduction from eating things such as zooplankton and particulates. These corals have to eat to be healthy! A recent study by Ferrier-Pages, et al. (2003) that was later confirmed by further testing found that corals that are fed grow their skeleton 30-75% faster, grow tissue 2-8 times faster, have more protein, have more chlorophyll and are in every way healthier and doing the things we want them to do faster than those that are not fed. Conversely, corals that are not fed suffer a precipitous drop in the amount of protein in their tissue and in their chlorophyll a concentration (Shick et al., 2005). A study by Sebens, et al. (1996) examined the differences in prey capture between two corals (Montastraea cavernosa and Madracis mirabilis). The Montastraea (relatively larger polyps) is known to catch a lot of food and to be very heterotrophic. The surprise is that the same sized colony of the Madracis (relatively smaller polyps) in a flume caught and ate 36 times as much food in the same span of time! Hmmm, seems to me like they need to be fed. Please do not take this information to mean that corals with small polyps need more food than corals with large polyps (let's not overcompensate now!), or you'll be missing the whole point. My intention is to illustrate that different species of corals show different food preferences, and that these preferences are not based on polyp size but rather on differences in each species' niches. It must also be noted, however, that a single species of coral can and will adapt to higher rates of heterotrophy or autotrophy depending on the conditions in which it grows (Anthony, 2000; Anthony and Fabricius, 2000). Corals often thought of as requiring bright light and little food can, and do, adapt in nature to conditions of low light with high food availability all the time.

The last major myth surrounding the term "SPS" is that these corals are all supposed to be very colorful and that if they are brown, something is wrong. This is nonsense. Many of these corals in nature are brown. Of course, it depends on the environment examined, and some places do contain primarily colorful corals, but not all places. Many locales have predominately brown and gray corals with the rare colorful one mixed in. These corals are perfectly healthy, their environment is just fine, and nothing at all is wrong with the situation. As many have discussed before, predicting coral coloration is often an exercise in futility. First, not all corals have the genetic machinery to be colorful, just as not all people have the genetic machinery to have blue eyes or red hair or grow to be seven feet tall. Beyond this, complex environmental and physical factors interact in ways that are still not understood to make corals either produce or not produce colorful pigments. Light is certainly a critical factor for the production of at least some coral pigments (Dove et al., 1995; Dove et al., 2001; Salih et al., 2000), while others do not seem to be induced by light intensity at all (Mazel et al., 2003). Both an additive (like internal reflectors) and a subtractive (like Venetian blinds) role has been assigned to certain coral pigments (Dove et al., 1995; Dove et al., 2001; Kawaguti, 1969; Salih et al., 2000; Schlicter et al., 1986). Mazel et al. (2003) argue that these pigments likely do not have a photoprotective role as has been suggested recently by Dove et al. (2001) and Salih et al. (2000). Personally, I find that the case has been well made that at least some coral pigments (certain GFP-like proteins-the "pocilloporins" of old) likely are playing a photoprotective role in certain corals (particularly in pocilloporids and acroporids) but also that certain other pigments (exemplified by GFP, green fluorescing protein) are not involved in this process. I think that, to an extent, each set of authors may have slightly overstated their positions. This leaves all the other coral pigments (and there are many) with unknown functions or cues inducing their production. Especially interesting are the pigments produced by azooxanthellate hard and soft corals. What purpose or function might these pigments have? While hypotheses have been offered, no consensus has been reached. The functions and the factors that induce the production of these and many other pigments in zooxanthellate corals are currently unknown, but in many cases light probably is not a factor (at least not directly).

Speaking of coloration, elevated concentrations of nitrogen (ammonium and/or nitrate) are often blamed when corals (especially Acropora but others as well) "brown-out." This happens through increases in the density of zooxanthellae in coral tissue and increases in the chlorophyll content of those zooxanthellae (making each one darker) (Hoegh-Guldberg, 1994; Marubini and Davies, 1996). To my knowledge, phosphorus (phosphate) has never been implicated in this process, though it has been shown to decrease calcification and linear extension when elevated (Ferrier-Pages et al., 2000). This makes sense because most algae (including zooxanthellae) are good phosphorus competitors and their growth rate or ability to overpopulate a coral is probably not limited by phosphorus in most cases. Many cyanobacteria, by comparison, are poor phosphorus competitors and good nitrogen competitors due to their ability to fix atmospheric nitrogen (Iizumi and Yamamuro, 2000; Kayanne et al., 2005). Zooxanthellae in hospite (living inside the coral), assuming their growth rate is limited by the availability of some essential nutrient, are more likely nitrogen limited than phosphorus limited, especially in tropical, neritic waters (see Klausmeier et al., 2004). The increased growth rate of most kinds of algae when nitrogen is abundant and phosphorus is limiting, plus the increased growth rate of cyanobacteria (N-fixers) when phosphorus is abundant and nitrogen is limiting (notice the two offset each other), creates the classic Redfield ratio observed in the ocean. For those unfamiliar, there is a highly perceptible trend for the ratio of available atoms of nitrogen and phosphorus in oceanic water (and often freshwater as well) to be 16:1, the same as the average ratio of those elements found in phytoplankton (Redfield, 1958). That brings up the topics of nutrient stoichiometry, resource competition, zero-net-growth isoclines (ZNGIs) and all sorts of other interesting interactions (nutrient stoichiometry and ZNGIs-Dr. Litchman would be so proud!), but those are for another discussion. The important things to understand are these: under normal circumstances phosphate probably cannot cause a coral to "brown-out" by stimulating the growth of its zooxanthellae (though it does have other negative effects and its concentration should be kept very low in the aquarium), and nitrogen (ammonium and/or nitrate) probably can cause this reaction in some cases.

A logical question is, does nutrient enrichment (such as that caused by human activities) always have a negative effect on corals and on reefs? The most ambitious project to try to answer this question was ENCORE (Elevated Nutrient on Coral Reefs Experiment) administered in the lagoon off One Tree Island in the Great Barrier Reef. Nutrient enrichment was simulated at each low tide by adding ammonium and phosphate to twelve microatolls. This nutrient-rich water was replaced with low-nutrient water from the ocean with every high tide. During the first year of the experiment ammonium was increased to a concentration of 10 mM (about 0.17 ppm-equivalent to about 0.6 ppm nitrate). The expected results (increased algal growth and biomass, decreased coral growth rates and reproductive effort, etc.) did not occur in most of the treatments. The next year the ammonium concentration was doubled to 20 mM (0.35 ppm-equivalently 1.2 ppm nitrate) (Koop et al., 2001). Some of the microatolls did show poorer coral health, but as Szmant (2002) has pointed out, this may be due to factors unrelated to nutrient enrichment. At 20 mM, this experiment also utilized nitrogen concentrations an order of magnitude higher than what is normally reported for even polluted coral reefs (Szmant, 2002). More moderate evidence comes from Marubini and Atkinson (1999). They enriched seawater with 5 mM nitrate (about 0.3 ppm) and saw no effects on growth rate in Porites compressa. They also tested the effects of lowered pH, which did decrease growth significantly (something for aquarists to keep in mind). Atkinson et al. (1995) also reported high sustained coral growth rates (and good health) in the corals maintained at the Waikiki Aquarium despite elevated nutrient levels: 5 mM nitrate, 2 mM ammonium, and 0.6 mM phosphate (about 0.3, 0.035, and 0.06 ppm, respectively). In this system pH was slightly low and alkalinity slightly elevated. Along these lines, while Marubini and Davies (1996) found that as little as 1 mM nitrate (0.06 ppm) could reduce the rate of coral growth, the effects of 20 mM nitrate (1.2 ppm) or ammonium (0.35 ppm) were eliminated by the addition of 2mM bicarbonate (Marubini and Thake, 1999). In other words, if the alkalinity was kept a bit higher than normal, the effects of nutrient enrichment, at least on growth, were undone. This lends support to the hypothesis that nitrogen enrichment decreases coral growth not because these levels of nitrate and/or ammonium are inherently harmful to the coral, but rather because at higher nutrient levels the two ongoing processes of calcification and photosynthesis compete for the same limiting resource: dissolved inorganic carbon, DIC. If seawater's alkalinity is raised slightly (by the addition of carbonate or bicarbonate), then carbon no longer limits either photosynthesis or calcification, nor is growth limited by this factor, either. To all the aquarists who think they get higher rates of coral growth with slightly elevated alkalinity: it looks like you're right! Do realize, however, that while these nutrient concentrations are elevated compared to most natural reefs, they are also at about the lower-level of detection for most hobbyist grade test kits. Based on this evidence it is my opinion that reef tanks are best maintained at or below these levels: 3 mM nitrate (about 0.2 ppm) and 0.3 mM phosphate (about 0.03 ppm). This is in comparison to less than 0.6 mM nitrate (about 0.03 ppm) and less than 0.2 mM phosphate (about 0.02 ppm) on most coral reefs (Kleypas et al., 1999).

Since reasonable quality test kits exist within the hobby and can detect even these relatively low nutrient levels, I find it curious that folks sometimes complain of "nutrient issues" as the reason their corals are not attaining some particular coloration, even when there are no signs of problem algae and nitrate and phosphate are both undetectable. Zooxanthellae, like any algae, can use inorganic sources of nitrogen only directly. If nitrate and ammonium are low in concentration, no other test, prayer or voodoo is required to affect the zooxanthellae, at least in terms of their ability to mask coral coloration. Nutrients are not hiding somewhere and somehow influencing the zooxanthellae. This simply is not possible. What is possible and is certainly the cause of browning are the many unknowns yet to be resolved in the understanding of coral coloration. The bottom line: brown is neither bad nor unnatural. Light and low dissolved, inorganic nitrogen sources affect this directly, but so do many other, unidentified factors.

For all these reasons, I find the term "SPS" to be utterly useless, often misapplied and to really hold back progress in both husbandry and care of many corals.

The Solution

To summarize, what we are currently doing is lumping all species of corals into five groups based primarily on their gross physical appearance. Certain characteristics have been assigned to each group describing what is supposedly its appropriate care. While mushroom polyps, zoanthids and soft corals do each represent valid taxa, the variation from family-to-family, genus-to-genus, species-to-species and even individual-to-individual is profound. Different colonies in each of these groups often grow in radically different environments with radically different environmental parameters compared to others in that same group, and they cannot be expected to do well (except due to most corals' innate ability to adapt) in a single, prescribed set of conditions. The scenario for large-polyped stony and small-polyped stony corals is even worse. All species of stony corals comprise the order Scleractinia. There is no reason to split this order into two groups with polyp size as the dividing characteristic. Polyp size in scleractinians does not determine light preferences, food preferences, water flow preferences, or any preferences whatsoever, nor does it even imply relatedness. The size of a coral's polyps actually has very little, if anything, to do with that coral's natural history and requirements. There is no natural divide in the continuum of polyp sizes. There is a smooth transition in polyp size from very small to very large in stony corals. Any dividing line is totally arbitrary.

These corals were all grown under power compact fluorescents. Polyp size doesn't necesarily say anything about a coral's lighting needs. Photos courtesy of Kirby Adams.

What is the result of adopting these faulty coral keeping recipes? In the best-case scenario the environmental parameters are actually a good analog of what that coral needs to be healthy, and it grows and lives fine. In a more moderate scenario the environmental parameters provided are not analogous to those in the coral's natural environment, but it manages to adapt and survive in the odd conditions (though it will never thrive the way it could in nature). Sadly, it is prone to major problems at the slightest hint of stress. In the worst-case and all too common scenario the coral simply fails to adapt to the inappropriate conditions into which it has been placed, and it dies. It has been estimated that Indonesia alone exports some nine million pieces of live coral per year, almost all of them headed to the U.S. I guarantee that at the end of a year there are not nine million new, live corals in this country. This is considering only Indonesia, not to mention all the other coral exporting countries. Sadly, a lot of corals die in captivity.

That, really, is the point of all this discussion: reducing coral mortality and increasing the hobbyists' rates of success (though these principles apply to any sort of organisms). After all, we all want to be successful hobbyists. No one enjoys or wants to cause coral mortality, both from an economic and altruistic view. I think we all can do something to effect positive change for ourselves as well as for others.

I always hate it when I hear someone speak about some issue or problem and then, at the end of the talk, he or she doesn't offer an adequate or implementable plan for how to fix that problem. I refuse to be "that guy," so here we go…

I propose that corals henceforth be described by genus (or best guess of the genus) and growth form (tabular, plating, digitate, etc.), where applicable, in any discussion about them whatsoever, but especially when related to their proper care. What really needs to be done is to shift the terminology because, by something as simple as referring to a coral in this way, we will dramatically reform the way corals are treated in captivity.

Let me use an example to illustrate what I mean.

Someone might come into the store where I work because he or she is having trouble with slow recession in the corals in their tank.

"What kinds of corals are having the problem?" I would ask.

"SPS-it's weird, my plate coral is fine," they respond.

Guessing that they are referring to a Fungia as the plate coral I inquire, "Do you know what genus they're from?"

"Acropora, they're all Acropora."

"Ok, how old is your tank and what kind of light and water flow do you have?"

"Oh, I've got 130-watts of power compacts-they're real bright-and two Maxijet 600s on a wavemaker, so it's good flow. The tank's a 20-gallon, about six months old."

"Ok, I think I know what's going on. Those corals are a bit demanding. Usually, you want metal halides for them to do best. The power compacts, while they look bright, aren't bright compared to the sun. Also, a little bit stronger water flow would be good for those corals. It wouldn't hurt to triple or quadruple that water flow for them. What would probably do best in there right now are other kinds of stony corals such as Trachyphyllia-open brain-or Euphyllia-frogspawn and hammer coral."

They would go home knowing what sorts of corals in particular would do well in their tank, which ones wouldn't, and why. If a particular genus is described as needing bright light or strong water flow, and some parameters are actually put on those subjective terms, people can enjoy a great deal more success. Instead of lumping hundreds of unrelated corals together, people would be more likely to succeed if each genus were referred to by name and if species (based on growth form) were treated differently in those genera that show large differences between species (e.g., Acropora, Montipora).

These terms also hold back success and progress for some other folks.

A reef hobbyist might be browsing in the store, saying he or she doesn't really like his or her tank because it doesn't look like a reef.

"What kind of lighting do you have and what do you have for water flow?" is always my first question.

"I've got six VHOs, a big return pump and a Tunze 6000 on a controller-that's on a 90- gallon tank."

"Hmmm, have you looked at these branching Montipora digitata?"

"I thought I had to have metal halides for SPS."

"Well, I usually prefer not to use that term myself just because so many different kinds of corals have small polyps. Some do best under metal halides; others such as these Montipora would do great under VHO lighting, and you have good water flow. They should do well for you." The next time I talk to this person they tell me how their Montipora is doing great and they pick up another fragment, this time a plating colony. They're excited that now their tank is starting to look like a reef. By using terms like "SPS," aquarists with tanks which are very well suited to inshore species, such as some in the genus Montipora, often do not attempt to house them, and instead often place these corals in a lot of light or water flow compared to where they usually grow in nature.

When people ask me a question and use the term SPS, LPS, softy, etc., I always ask if they know more specifically what kind of coral they are talking about. If they don't, I answer their question as thoroughly as I can, but also explain to them why I can't answer the question very well without knowing what kind of coral we're talking about. Then they understand why it is so important to know at least the basics of coral identification. The above terms just aren't good enough to tell us much of anything about a coral. When I refer to a coral I always use the name of its genus (and species, if known, e.g., Euphyllia paradivisa). I try to include a common name when talking with new hobbyists, so they aren't shell-shocked, but I use the scientific name as well.

If someone is interested in soft corals, I explain why some species are very easy to care for while others (primarily azooxanthellate species) are very, very difficult. While I use the genus name, it is often a best guess (e.g., "Well, it's probably Capnella or Litophyton-but it could be something else, too."). It's lucky for us that most soft corals are so adaptable.

I do the same thing when referring to stony corals and include differences in growth form where applicable. If someone wants to keep a bright pink Seriatopora in a tank with very strong water flow, I make sure they understand that this coral (with its fragile branches) usually grows in somewhat calm areas. If someone wants to keep Acropora colonies, I make sure they understand that digitate colonies need very powerful water flow, whereas thinner branched colonies do not. Imagine all the information (information critical to success with these corals) that would be omitted if I referred to corals just as SPS, LPS, soft, mushroom polyps and zoanthids.

The solution to this problem is simple and is something that most advanced hobbyists already do most of the time anyway. The terms mushroom polyp, zoanthid and soft coral are all valid, but we should not think and should not give the impression that these terms provide any information about the proper care of these corals. They do not. The terms SPS and LPS are not valid terms, and it would be best for everybody if they just dropped out of reefkeepers' vocabularies. Just don't use these terms at all. I don't, except when other people bring them up. In that case I ask what kind of coral they mean because those terms don't tell me anything, and I let them know that (nicely). Eventually, they just stop using those terms with me and refer to corals by name, and I would bet that they do the same with most other people. Let us all simply refer to corals by using their scientific names-that is, their genus, or as close a guess as we have-and growth form for very diverse genera such as Acropora and Montipora. Let us also completely stop using the terms SPS and LPS, and use the terms mushroom polyp, zoanthid and soft coral only for basic identification, not for describing care.

There are a lot of people in this hobby. Most folks are new, or nearly new, and get perhaps a year or two of experience under their belts before dropping out due to the perceived difficulty. I can't help but think we all do these hobbyists, as well as ourselves, a huge disservice by using coral keeping recipes that are obviously outdated. The knowledge about these animals is available, but it must be seized, nurtured and spread. By continuing to use these terms and acting as though they give any true meaning to the discussion, we cling to and spread ignorance. Isn't it about time that we all take the tools and knowledge that we have and use them to move forward? Isn't it time to scrap a faulty system that gives poor results as often as good ones? I think so, and I know that we all would be better off for it.

If you have any questions about this article, please visit my author forum on Reef Central.


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