The Holding, Shipping and Transport of Corals, Part 1:
Shipping and Transport

It is well known that a large percentage of the mortalities to marine ornamental organisms happens during the numerous transportation and shipping processes that occur after collection or harvest. Despite the high mortality rate, shipping processes are rarely studied to limit mortality and thus decrease the impact that aquarists have on coral reef species, or to limit financial losses incurred by those involved in the trade of tropical marine species. This article discusses various aspects of, and limitations to, the knowledge of shipping practices involved with the transport of corals and other marine species.


For the first fifteen years that I visited coral reefs, my experiences were limited to many reefs throughout the Caribbean, the Gulf Coast and Hawaii. At none of the places I visited were coral banks exposed at low tide, and the intertidal zones consisted of small tidepools and rocky shores where only a handful of marine ornamental species could be found. Even seeing photos of them in books doesn't quite prepare one for the spectacle of exposed reef flats found in the tropical Indo-Pacific. To actually stand in 35°C heat at noon on a cloudless day on an exposed coral reef is an eye opener. Corals, bivalves, gastropods, algae, echinoderms, seagrasses, sponges and other fauna are completely exposed to air, hot sun, rain and all the elements of a nearly terrestrial existence for many hours each day. Even fishes are found in small pools of water that are heated to extraordinary levels and periodically deluged with freshwater from rainfall, or exposed to very high salinity from evaporation; conditions that would never be found in a marine aquarium. Yet the myriad life forms of these exposed reef tracts do not die or desiccate. They all have adaptations that allow them to survive the daily exposure. Soft corals collapse and contract. Sea cucumbers also contract and lie motionless. In fact, most organisms remain in some sort of stasis, clamped closed or remaining relatively motionless, often bathed in moist mucus or having a tough epithelium or shell that allows survival in these hostile conditions. Probably few people would set their corals and tridacnid claims atop the rim of their aquarium and walk out the door to go to work, returning each evening to place the animals back into the water. Yet this is precisely analogous to what happens on many tropical reefs and in intertidal zones all over the world.

During a trip that took my wife and me to a seldom-visited coral bank called Tanajampeiah, somewhere between Sulawesi and Flores, we snorkeled onto an atoll beach through a break in a nearly continuous hedge of Acropora that was exposed by at least a meter. It was literally like walking through a hedge of holly bushes as we waded when the water became too shallow to swim. On Menjangen Island in Bali we walked the rocky beach at low tide, finding it impossible to walk without stepping on the thousands of Tridacna crocea that lay exposed on our "reef foot path." A few years earlier I was forced to crunch my way across many meters of a solid thicket of Montipora digitata mostly exposed to air in water that was nearly 40°C to reach a patch of atoll sand on which I could stand. Below is a series of images of exposed coral reef from various places throughout the Indo-Pacific. The variety of organisms should be noted as including all types of corals, sponges, algae and other invertebrates. The relevance of these observations of entire coral reefs being exposed daily at low tide is that many animals can and do survive exposure to air, heat, freshwater and other stresses without dying. It is a normal condition in the field, and therefore should not be taken as a shock when I suggest below that shipping many corals and other invertebrates is possible without submerging them in water.

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Photos by Eric Borneman.

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Photos courtesy of Helmut Schumacher.

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Acropora valida exposed at low tide in Tonga.
Photo courtesy of Anthony Calfo.

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Photos by Eric Borneman.

On a topic very different from exposed coral reefs, very few things are as predictable, disconcerting and annoying as picking up boxes of livestock that have either been delivered or picked up at airports. I have only very rarely received livestock boxes that are not at least a bit damp on the bottom. At the other end are boxes that are clearly crushed, with streams of water pouring from their corner as I carry them inside. With the exception of fish and a handful of invertebrates, however, I am almost always surprised to find that livestock in bags that have leaked, even when completely devoid of seawater, is often alive and well. Equally predictable, and often surprising, are the numbers of shipping bags containing water that are fouled with animals that have died in transit. If coral reef organisms can stand the natural abuse mentioned previously, why is there such a high mortality rate during shipping? Why are some species considered to be "poor shippers?" What if the shipping cost of our livestock that required overnight or airfreight couriers were not spent mostly on shipping water?


One of the first articles to focus on coral transport was by Edward Bronikowski (1982). In the article he discussed transporting corals using both "wet" and "damp" techniques. This article is worth discussing in some depth, for it illustrates just how little we have learned and how much has been done without making an appropriate impact. It is especially relevant since after its publication, other well-known authors have mentioned and confirmed the described method's utility (Sprung and Delbeek 1994, Carlson 1999, Borneman 2001).

Bronikowski described a catchall marine tank at the Cleveland aquarium that lacked corals because of their inability to obtain specimens that would arrive in good condition after shipping. That aquarium's success changed remarkably after contact with none other than marine aquarist Dick Perrin, founder of one of the first coral farms, Tropicorium. It is important to recognize that the year was 1982. The Berlin method had not yet come into vogue, and another ten years would pass before American hobbyists would even begin to have widespread success in coral husbandry. It is also significant that Mr. Perrin was already succeeding in propagating corals, not just getting them to survive. His suggestions preemptively echo my observations above; 23 years earlier, in fact. He is described as having similarly bad experiences with corals shipped in water. On one occasion a box had been broken and the water from the shipping bags lost. The bags with water contained mostly corals in a "coral bouillabaisse," while those in the bags that had lost their water looked healthy and extended their polyps immediately after being placed into the aquarium.

Bronikowski then attempted shipping corals from Florida numerous times using various methods. He found that any amount of water left in the shipping bag resulted in coral tissue death. He went so far as to stuff pantyhose with perlite in order to absorb any water in the shipping bag, even after the coral was "drained" by allowing it to sit exposed for awhile after collection. Shipped colonies were placed on a Styrofoam platform to prevent the colony from sitting in any water. Only then did they experience the highest success rates with transport times of 14 hours. They also found that "hitchhikers" survived well in the drained residual water pools, including worms, crabs, shrimp and brittle stars.

After combining metal halide lights, strong circulation and "low" nitrate levels of 20mg/l-1 achieved through water changes, the Cleveland Aquarium finally achieved success with corals. Today, all of us are extremely familiar with the importance of light to coral health, most are aware of the importance of strong water flow (though many still do not actually provide adequate water motion) and 20mg/l-1 nitrate would now be considered a highly aberrant reading, with a majority of aquarists able to maintain nitrate levels that are nearly unmeasurable by standard hobby test kits. We have listened, learned and practiced the lessons described in this 23-year-old article, except one: almost without exception, corals today are still shipped in water.

As Ron Shimek noted in a personal communication, "When I wanted to ship various marine animals from the UW Friday Harbor Labs to various researchers around the US in the early 1970s, I contacted one of my professors, the late Paul Illg. He advised the most sure-fire way to ensure success was to ship the animals "damp, but not wet." If possible, wrapped in some sort of kelp (moisture insurance) in plastic sacks. The animals were kept in an atmosphere of 100% relative humidity. For most animals, this allows the gases to diffuse across the moist respiratory surfaces easily. If the animals are in water - any water - the gas has to diffuse from the animal into the water and then from the water into the air, and vice versa. This diffusion is fast enough if the water layer is very thin, but if it is thick - as in a bag - diffusion of oxygen from the air into the water is too slow to replace what the animal is removing from the water, and the animal smothers. The converse for carbon dioxide occurs, as well. The critter gets a double whammy, all due to the bag of water. Anyway, the point is that Illg learned this shipping method in the 1930s(!) and had been using it since then. It was well known in the invertebrate zoology circles that I "ran" in that one did NOT ship live animals in water and expect much survival."

Corroboratory Stories

In 2003 I made several collection trips. The first was to Belize, where I collected several fragments of Acropora for culturing. After breaking their branches, I left them hanging in the water tied by a fishing line from a tree branch overhanging the lagoon side of a small coral caye. They lived in apparently perfect health for several days before I was to return to Houston. I was already concerned about what would happen to these sensitive species in a bag of water, so I wrapped them in wet plastic strips and a small amount of water to keep the strips wet, and placed them into 50ml centrifuge tubes. Twelve hours later I arrived in Houston, and the corals had either completely sloughed their tissue, or finished sloughing all their tissue by the next morning.

Later that year I brought back several boxes of numerous species of coral shipped "dry," without draining, simply sealed in plastic bags. All corals survived the transport process that was approximately ten hours in duration. Only Oculina spp. seemed to suffer slightly from this mode of transport, and none of those had total colony tissue loss. In early 2004 I made another collection, and this time drove the corals to Houston in open-top tanks. The trip's total duration was approximately 16 hours and while most corals fared well, some started to slough their tissue within several hours of collection. However, in this case the sloshing of water in the tanks while driving created quite a bit of water motion, and oxygen levels probably remained high because of the shallow tanks and their exposure to air. I believe these factors contributed to the general success of this shipment.

In 2004 I was contacted by Lee Goldman in Guam who was rearing corals from spawn. We decided to attempt trial shipments to determine the best shipping method to ensure survival, and I was also already beginning to take oxygen measurements in closed systems (Part 1, Part 2, Part 3). While I found that oxygen levels in shipping water remained high in bags topped with oxygen, the oxygen level of water topped only with air dropped precipitously. Based on speculation of the effectiveness of breathable bags, and concerned about temperature, I sent Lee a number of Evert-Fresh "breathable" produce bags and temperature loggers. His first shipment to me of a handful of corals (Acropora and Pocillopora) was less than ideal. Despite transporting the small colonies in large volumes of water with an oxygen cap, only about 50% of the shipped colonies were alive, and another 25% were partly or wholly bleached. Part of the trouble may have been the temperature, which was extremely low because of an ice pack that was wrongly placed among the corals, leading to water temperatures in bags adjacent to the ice pack around 19°C. Not all bags were that cold, however, and some colonies with warmer water also had either bleached or sloughed their tissue in transport. In contrast, a later shipment whose corals were wrapped only in seawater dampened paper towels resulted in 100% survival. In a recent conversation with him, Lee told me of another shipment he had sent to Fernando Nosratpour, the senior aquarist at the Birch Aquarium at Scripps, San Diego. In this case the corals arrived in Los Angeles within 24 hours, but were held up in San Diego for another 24 hours. Despite spending two days wrapped in a wet paper towel, the colonies survived.

In October of 2005 several more trial opportunities arose. First, because of hurricane Rita, a member of our aquarium club, MARSH, had given me his corals to hold for him since he was evacuating for the storm. He brought over several dozen corals including several partially bleached Acropora species in water that had become a bit warm, though not excessively warm. The next day those few stressed species sloughed their tissue. Sometime after Rita I returned his corals and included a few fragments of other Acropora from my tanks to replace the three fragments that had died. I wrapped them all in seawater dampened paper towels and placed them into small Tupperware-like containers, then drove to my lab where I was meeting him. We also worked on our club's salt study for many hours and by the time he placed the corals into his tank, they had been out of water for eight hours. He later remarked that they all survived and were extending their polyps almost immediately, but admitted he had been surprised at how I had packed them.

In a second recent trial I was in Belize during October 2005, and had permits to collect Acropora cervicornis and A. palmata. Knowing the difficulties I had experienced in previous shipping attempts, I tried very hard to maximize their chances for survival based on past experiences. I knew that, in particular, A. palmata would need to have very expeditious transport once removed from the water. My wife and I broke fragments on Southwater Caye and again tied the fragments with fishing line and suspended them in the water column underneath a dock to allow them to be flushed with ocean water and hopefully recover somewhat from the stress of being broken. Eighteen hours later we cut the fragments loose and quickly wrapped them in wet paper napkins and put them into a Ziplock bag. Five hours later, by boat and then by car, we arrived at the Belize City airport. Another six hours later we arrived home and they were put into a culture system. Several of the A. palmata fragments were slightly bleached, but most looked good, and all the A. cervicornis fragments looked just as they had when we had removed them from the ocean. Today all are alive and doing exceptionally well; the polyps extended on all fragments of both species within hours (at least) to a day (at most).

I also brought fragments to MACNA XVII in Washington D.C. in a similar manner, again with all surviving. Only once has the "damp" method of shipping not worked well for me, and I am currently trying to address whether there were other factors involved in that case.

Other Shipping Issues

For articles published in recent editions of Reefkeeping Magazine (Part 1, Part 2, Part 3), I measured oxygen levels in bags containing seawater and in bags containing corals and seawater. I tested both standard plastic and breathable bags, and found that oxygen levels remained high in bags where an oxygen cap was used, but dropped quickly when only air was in the bag. The respiration rate, ratio of water:air/oxygen and length of shipping time all obviously affect oxygen levels maintained over the transport's duration. However, in only one case did oxygen levels drop quickly and precipitously in a large volume of water opened to the air, and that was during the presumed bacterial bloom in a tank after its live rock had been removed. The water became cloudy and oxygen levels dropped greatly. I presume the bloom was caused by heterotrophic bacteria, since the tanks were lit by ambient room light and a fluorescent light, and autotrophic microbes (bacteria and/or phytoplankton) would produce, not consume, oxygen in the presence of light. This is relevant to the number of shipping bags that arrive with cloudy water in them.

As I have written in the past, corals, and indeed, all species with a mucus-covered epithelium - a trait that probably includes the majority of species in the trade - also have a productive bacterial flora that utilize the mucus as a nutrient substrate. As such, mucus in a small water volume essentially turns a shipping bag into a nutrient broth that cultures microbes at logarithmic rates. It is little wonder that so many bags become fouled in transit. It is also little surprise that species known to produce copious amounts of mucus, such as Xeniids and Acroporids, are often the most sensitive to shipping and to fouled bag water. In such cases it does not matter whether there is an oxygen cap or not because the rate of respiration is greater than the rate of diffusion from the cap of gas into the water, as evidenced in the tank trial described above.

While mucus has some detrimental effects on submerged coral specimens, it also acts to keep tissues moist in exposed specimens. Mucus is primarily what allows the coral reef species, including corals, to survive exposure at low tide (although methods of preventing desiccation may involve other traits and behaviors, as well, including shells, scalloping, contraction, color patterns, burrowing, etc.). By shipping corals "damp" or "dry," mucus production acts beneficially, as it does in the wild, instead of detrimentally, as it does in shipping bags of seawater.

In the case of shipping corals wrapped only in a damp, porous, breathable paper, the rate of diffusion depends only on diffusion across the mucus from the air, and not through water. Furthermore, the oxygen levels in air are much higher than in oxygen-saturated seawater. As a corollary, many shippers use strips of plastic in shipping bags. I have heard it said often that this practice is done so that the strips act as a "cushion." I am not sure how plastic strips a few microns thick act to cushion submerged specimens, but I do know that plastic does not "breathe" very well. In fact, when shipping corals wrapped in wet plastic, the plastic tends to adhere by surface tension to the corals' wet mucous surface and prevents oxygen from reaching tissues locally wherever it contacts the epithelium. In many cases I have experienced, the wet plastic has caused local tissue loss, as well.

A potential downfall of shipping out of water is that seawater has a very high heat capacity and acts as a good insulator against temperature change. I had long been curious about what happened to temperature inside shipping boxes as they were placed into cargo bays of planes that were not climate controlled, or as they sat outside in cargo areas exposed to excessive heat or frigid cold. On more than a few occasions I have received boxes whose cold-packs or heat-packs had been exhausted and whose bag water was out of the acceptable temperature range, both too hot and too cold. While I am unaware of any sure and economically feasible solution to temperature issues over extensively long transit durations, I have acquired some data to reveal what happens to temperature inside shipping boxes over average shipping durations. I have sent temperature loggers to numerous people to enclose in Styrofoam boxes while shipping corals, both domestically and internationally. I have also measured temperature while conducting spawning work inside an igloo cooler exposed to direct tropical summer sun for over 48 hours.

The temperature loggers produced the following plots, with explanations of each case under each plot.

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This log shows a shipment from Mitch Carl (Omaha Zoo) to Bruce Carlson (Georgia Aquarium) beginning 7-29-2004 at 1300 hours, arriving at 0900 hours on 7-30-04. Bruce Carlson reported a temperature of 25.1°C upon opening the box.

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This log shows a shipment from Mitch Carl (Omaha Zoo) to Joe Yauillo (Atlantis Aquarium, New York) beginning 7-29-2004 at 1300 hours, arriving at 1000 hours on 7-30-04.

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This log shows a shipment from Lee Goldman (Guam) to Eric Borneman (Houston, TX) on 8-17-05 (+1 day) at 1400 hours, arriving at 1300 hours on 8-17-05.

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This log shows a shipment from Lee Goldman (Guam) to Eric Borneman (Houston, TX) on 8-17-05 (+1 day) at 1400 hours, arriving at 1300 hours on 8-17-05.

Additionally, three other temperature loggers were put into boxes from Florida to Houston, from Puerto Rico to Houston and from the Omaha Zoo to Houston. Unfortunately, I spilled seawater onto those data plots, the papers stuck together and I can no longer use them. In each of the plots, however, no remarkable changes occurred inside the Styrofoam containers, no heat or cold packs were used and the temperature stayed well within the range necessary for corals to survive. In the case of the Omaha Zoo to Houston shipment, I do recall that the plot was almost completely stable from Omaha up to the point when the box went onto ground travel by Federal Express. At that point, but at no time in flight or at the airport, its temperature slowly increased by about 1-2°C over the 2.5 hour delivery time from the airport to my house. In the case of the Guam to Houston shipments, there is clearly a very strong temperature decline to levels where the soaked temperature loggers came in contact with a bag of ice set into the boxes (see text above). In one case, where I was conducting work on coral larvae in a large Igloo cooler on a ship's top deck in full sun and with ambient air temperature well over 35°C, the water temperature was around 30°C and remained at this level with the lid closed for 48 hours. From these trials it seems as though Styrofoam coolers, if sealed, act as efficient thermal insulators to marine species shipped in seawater.

To restate the above, I have received sealed Styrofoam boxes whose water temperature had become too hot or too cold, but without temperature loggers present. It is difficult to say whether the aberrant temperature was due to outside temperatures or to the use of heat and cold packs. The marked drop in temperature in the Guam to Houston trials resulted not from exterior temperature conditions, but from interior temperature conditions (ice pack). In a subsequent shipment from Guam, corals were sent "damp" in seawater soaked paper towels and placed into shipping bags with air only. The ice pack in this shipment was properly placed by taping it to the inside lid of the Styrofoam container. It had completely melted by the time I picked up the box, and yet the inside of the box was neither too hot nor cold, and the corals shipped very well. From the trials above it seems as though that under normal shipping durations and at least from hot to hot areas (e.g. summer in Omaha, Houston and the tropics), it is possible to maintain adequate temperatures using only Styrofoam boxes. Therefore, it is also likely that it is possible to maintain thermal control whether or not species are in water or out of water under normal shipping durations (from trials above) and possibly much longer, based on the survival of Acropora and Pocillopora during the 48-hour period from Guam to Scripps.

Summary and Conclusion of Part One

Over the years aquarists are quick to pick up new knowledge and new technologies that improve the health and survival of marine ornamental species, especially corals. Given the documented successful shipping of corals for over 20 years using "dry" or "damp" shipping by professional aquarists and researchers, and the frequent loss of species shipped submerged in stagnant bags of water, why has the aquarium trade been slow to embrace these methods? I suspect it is because most people have never seen vast tracts of coral reefs exposed to air, heat and rain, and because it seems to be an unnatural condition for corals to be out of water. Many hobbyists on Internet forums regularly ask me if their corals can tolerate brief periods out of water. With few exceptions I regularly take corals out of my systems for propagation, sampling and photography. I have no qualms at all about leaving corals sitting on a countertop for up to an hour, either totally exposed to air or with a damp paper towel over them. I have left some specimens, by inadvertently forgetting about them, on the tank's edge for many hours under metal halides and with a fan blowing across them, only to find they extend their polyps quickly after submersion. On the other hand, I have taken coral fragments and put them into a small container of water, only to find them dying after the same length of time as those that were exposed.

I am not suggesting that either method is infallible, or that all species have equivalent tolerances to stagnation or exposure. However, the evidence strongly suggests that "damp" shipping is a better way to ship corals to ensure their survival, another advantage of which is the reduced shipping weight without large quantities of seawater. I tried to explain this to the owner of a wholesaler in Fiji, Waterlife Inc., who said that he had particularly bad success shipping Acropora. When I suggested he try shipping "damp," he wouldn't hear of it and dismissed the idea curtly and completely. However, he also seemed to have had poor success maintaining them in his facility, and perhaps the corals were already too stressed to successfully endure the shipping. On the other hand, some facilities seem to have nearly perfected the technique of shipping in water. Still, if the success rate is good, and if it is equally good when shipping without water, the cost savings alone in freight charges should make a strong case for change. If nothing else, more controlled trials should be attempted in order to determine which method allows for the greatest survival and in which species. It seems to be a pragmatic economic and conservationist approach for all involved.

For those species with attached flora and fauna because of collection on live rock, shipping in water seems to pose an even greater problem through fouling of bag water. Attached or encrusting soft corals and corallimorpharians are good examples of species attached to substrate that often arrive in cloudy bags of water and in poor condition. In fact, live rock with attached corals, sponges, urchins and bivalves that I received from Gulf View arrived in sealed Styrofoam boxes and with the rock wrapped in wet newspaper. The life on the rock survived extremely well, including the aforementioned organisms after a transport time of nearly 20 hours.

I plan to continue to conduct shipping trials and document the results over the coming months and years. As I accumulate more information I will present it again at some point in the future. My next article will discuss issues with livestock holding protocols, and provide suggestions on how to improve health and survival of ornamental species to the trade.

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


Borneman EH. 2001. Aquarium Corals. TFH, Neptune City, NJ. 464 pp.

Bronikowski, EJ. 1982. The collection, transportation, and maintenance of living corals. AASPA Annual Proceedings: 65-70.

Carlson, BA. 1999. Organism responses to rapid change: what aquaria tell us about nature. Am Zool 39: 44-55.

Sprung, J and Delbeek, JC. 1994. The Reef Aquarium. Ricordea Publishing, Coconut Grove, Fl. 544pp.

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The Holding, Shipping and Transport of Corals, Part 1: Shipping and Transport by Eric Borneman -