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Dendronephtya Aquarium.Net Dec 96

This month Eric Borneman tells us why Dendronephthya shouldn't be kept in an aquarium. December 1996 Index for Aquarium Net, Aquarium Net has numerous articles written by the leading authors for the advanced aquarist


By Eric Borneman

The Carnation Corals (Christmas Tree, Cotton, Soft Tree, Cauliflower Soft)

Phylum: Cnidaria Class: Anthazoa Subclass: Alcyonaria Order: Alcyonacea Family: Genus: Dendronephthya Species: rubeola, mirabilis, aurea, others

The members of the genus Dendronephthya are quite possibly some of the most beautiful corals in all the world. They can exist in spectacular arrays of color and, when expanded, present a gaudy array of spiky polyps. It is no wonder that they appear with such frequency in stores across the country. However, this temptation of color and beauty is very misleading. All members of Dendronephthya are extraordinarily difficult to keep in captivity, and their purchase should be avoided .

Unfortunately, the lack of survival of many corals leads the hobbyist, both beginner and advanced, into a world of unknown variables and theoretical dilemmas which give rise to more basic problems discussed herein.

The Carnation corals, as they are most commonly referred, are a large group of soft corals found throughout the Indo-Pacific. They are particularly common throughout the Red Sea. Another interesting fact I have stumbled across is that Dendronephthya reproduces all year round, continuously.

They are exclusively ahermatypic, meaning all species lack zooxanthellae required for photosynthesis. Without the symbiotic algae, these corals require a continual wash of phytoplankton across their polyps in order to survive. Dendronepthya hemprichii, sinaiensis and Scleronepthya corymbosa have been found to be almost exclusively phytoplankton eaters, and to actually capture very little zooplankton. This makes complete sense, since phytoplakton is smaller, easier to capture, and these soft corals have relatively undeveloped stinging cells. Thus zooplankton, as previous thought to encompass their main diet, would be hard to capture with such "wimpy" nematocysts. Indeed, captive conditions may be possible using a regular feeding of phytoplankton, however, the amount of food required would still be extraordinarily difficult to cope with in a closed system.

Most ahermatypic corals are found in shaded or mostly shaded areas of the reef. Though most Dendronephthya are indeed found in the wild under ledges, overhangs, and in caves, many specimens can also be found on reef slopes in full sunlight. This is especially true for those examples found in the Red Sea. Thus, light does not seem to be harmful to some species, despite a preponderance found in dimly lit areas.

The sclerites of Dendronephthya are particularly needle-like. They are visible when the coral is collapsed and not feeding. With a strong light, they are also visible through the translucent tissue of an expanded specimen. It has been supposed that the sclerites, which protrude from the coral in the collapsed state, may help facilitate gas and water exchange. This seems likely, since these corals expand tremendously and must be able to have a capable system that allows for such enormous inflation with water. It is hard to imagine how such an unimpressive lump of tissue can become such an elaborate display of feeding branches, but I suspect that elastin or another proteinaceous elastic compound must be a major component of the exterior tissue walls. The energy expenditure needed for the active transport of substances across cell membranes to the interior of these corals and the concomitant passive transport of water must be significant. Without photosynthesis, these corals would likely require a significant planktonic input for enough energy just to allow for these daily rhythms of contraction and expansion. Seemingly, there would be little energy left for growth, and this is exactly what is found. Because of their capability for dramatic expansion, little tissue growth is necessary to produce specimens that, when expanded, can attain very large sizes. Thus, some of the enormous specimens seen in the wild which are quite old, in fact consist of fairly small amounts of growth in terms of an increase in actual physical mass.

In the aquarium, all the amazing properties of Dendronephthya become insignificant. Why? Because they don't survive. Despite massive importation of these corals, many refuse to expand even once upon introduction to captive conditions. They remain in a collapsed state until the tissue dissolves away. Some specimens may adopt a more Goniopora-like pattern where they may expand well for a time, and then slowly begin to expand less and less until they have wasted completely away. Of course, like many corals, there are occasional sitings and claims of hobbyists who have kept Dendronepthya alive for years. I have never personally known this to be the case. In any event, I believe the factors which would allow for the success of this coral in aquariums, even if the claims were true, would be incomplete and not reproducible. It seems as though very heavy feeding of zooplankton and detritus, strong continuous and non-laminar current, and adequate placement with regard to light would be essential to their survival. In any situation where such heavy feeding must occur, there is the downside of having to somehow dispose of the high nutrients that would predominate in such a closed system, either mechanically or biologically. Wilkens has suggested that heavy skimming and heavy feeding has allowed him to keep certain species for a period of years in systems designated almost exclusively to the needs of these and similar corals.

However, it has not become the goal of captive reefkeeping to merely allow for an animal to survive for a short length of time. The specimens must be able to survive, grow, and hopefully reproduce in captivity. I feel that any attempts outside these guidelines is an exercise in futility, and a deleterious mismanagement of life and ecosystem. It is my position that not only should these corals not be attempted to be kept in captivity at the present, but every effort should be made by responsible aquarists to inform dealers and suppliers to stop the harvesting of these dazzling corals for the aquarium trade. Hopefully, advances in the hobby, such as the use of refugia to provide natural sources of plankters, and the proliferation of habitat style tanks, will allow the contents of this article to be proven false in the future. With some work, Dendronephthya may one day become a commonly aquacultured coral and a welcome addition to an aquarium. However, hobbyists should not succumb to allusions that others are keeping this coral with any degree of success, nor to illusions that they are capable of prevailing with no basis besides an otherwise thriving reef community.

There have been so many advances in the reefkeeping hobby in the past several years, most of which are unknown to beginning and intermediate hobbyists. This brings up what I feel to be a grave and unfortunate occurrence within the community of reefkeepers. Despite rapid advances being made, the influx of new captive reefs by beginners is far outpacing the dissemination and availability of current knowledge. Through my work with several online communities, I am in a unique position of being able to glean from a huge, often international, cross section of hobbyists. In my dealings with countless hundreds of hobbyists, I am regularly confronted with people who are still using undergravel filters, and are still unaware of the concept of live rock as a filter, though they have plenty of high quality rock in their tanks. It has become obvious that no matter how many books are available and how many articles are written, the majority of people unfailingly believe whatever the uninformed retailer tells them to be true. And the retailers are telling them to buy Dendronephthya .

At the recent MACNA conference in Kansas City, the stratification of hobbyists and the esoteric nature of the people present was quite obvious. Yet, a wide void exists between the small percentage of advanced hobbyists and all the rest of the people keeping reefs. Every day, hundreds of people go home with equipment and supplies to start a reef tank, while the leaders of the hobby are taking PAR measurements, calculating the spectral characteristics of metals like Iridium, and beginning the development of new and expensive products. Books, magazines, and other information sources that publish the advanced findings are either too complicated for someone without a scientific background, or are priced so high that it is impossible to convince a beginner to spend the money on these helpful resources. The serious hobbyists are predominantly the only ones willing to pay large sums of money for books with information that, for the most part, they already know. They are the only ones willing to diligently plod through articles written so mundanely that even really advanced hobbyists have a problem keeping their eyes open while reading. I feel it is the responsibility of the advanced hobbyist to continually and patiently drum into the newcomers in the hobby basic information that they wrongfully assume to already exist. Books should be priced so they are affordable to those who need the information most. Articles should be easy to read, to the point, and lacking in the sarcasm and intolerance that seems so prevalent among the members of the reefkeeping elite. Indeed, the perfusion of knowledge, skills, and equipment should be emphasized over the motivation of profit that shows itself, for example, in the distribution of products and literature through companies whose ethical standards are contradictory to the supposed views supported by the makers or writers of those products. There is no reason that good products and proper livestock cannot be the means of profit for all people and places. However, so long as cyanide and dynamited reef creatures comprise the lowest priced available species, and retailers charge upwards of six dollars per Astrea snail, there will be wanton destruction of species and inappropriately stocked aquaria. So long as what is obvious to the advanced hobbyists is unknown, unavailable, or out of reach to the beginner and retailer, the advances made in the hobby may turn out to be fruitless.

The result is predictable. Most stores cannot afford to keep the advanced and high quality products on their shelves. Most people cannot keep up with the advances in the hobby until many animal's lives have been lost. When the capability to successfully care for Dendronephthya arises, it should be made known to everyone, and not only through cryptic scientific passages and the all too often ego filled comments of advanced reefkeeping forums. The benefits to the hobby, and the reef itself will then become patently obvious to everyone. After seeing the tragic destruction of reefs by human means on my recent trip to St. Lucia, I was reminded of all of our responsibilities to the natural environment on which we depend for our studies and enjoyment. As long as there are irresponsible retailers putting inappropriate species such as Dendronephthya "at unbeatable prices" in national magazines, and as long as I hear fish stores recommending species because of intentionally damaging profit motives or simple misinformation, and as long as "guru" reefkeepers do not have the time to deal with such lowly people as beginning reefkeepers, I will continue to offer any help I can to those who are confused about the care needs of any animal offered through the hobby. I hope that I can one day happily retract the content of this article by announcing information that allows the widespread capability to successfully manage Dendronephthya , and other similar species, in captivity.

Until next month... Eric Borneman

Created by liquid
Last modified 2006-11-23 01:36