Challenges of a Coral Reef Aquarium
Suzanne M Gendron
Modern Society no longer wishes to see small aquariums with single animals. In addition, with the increased world wide pressure to save our coral reef, protect our natural resources and establish in-house breeding programmes, Aquariums such as Sea World Indonesia are working towards exhibits that are naturalistic, educational and conducive to allowing the inhabitants to reproduce.
This holds true for fishes, sharks and even corals. At SeaWorld Indonesia, the 543 display for our live corals is one such attempt to reach that goal but it I not as easy as filling a tank with saltwater and adding live coral.
Discussion with regard to the special needs of live corals in closed systems and a survey of what is being accomplished at SeaWorld and throughout the aquarium industry will be presented.
The challenges of a live coral reef aquarium are many. First challenge: should live corals even be displayed? Corals are one of the protected animals under CITES. Another challenge is: how does one obtain corals for oneís coral reef aquarium? And how does one keep these beautiful jewels alive away from the ocean? But maybe our biggest challenge is deciding: what role the modern aquarium plays in this drama?
To define what is a "modern aquarium", we should understand where aquariums began. They trace their beginnings to the ornamental ponds and ceramic bowls where Chinese Emperors kept their prized fish. It wasnít until much later in the early 1800ís that large public aquariums were built, such as the Londonís Crystal Palace Aquarium, built in 1851 and the Paris Exposition. Focus was on the individual fishes in sterile glass cages.
Modern Aquariums now design exhibits that are part of a naturalistic eco-system, with many different animals living together. They focus on education, conservation, scientific study and recreation. The driving force behind this change of focus was the increased world-wide pressure to save our coral reefs, to protect our natural resources and to establish in-house breeding programs to assist with conservation efforts in the wild.
The role of zoos and aquariums in our modern society is to be the leaders in this; influencing their communities and visitors to participate in conservation, to care about the animals that share this planet Earth and carefully manage our precious and dwindling resources. We have a moral obligation to keep our animals healthy but also, if our exhibits and animals are not well cared for, healthy and exhibited well, they will negate the messages we are trying to convey.
SeaWorld Indonesia has chosen to direct much of itís efforts to highlighting the status of the coral reefs in Indonesia. Preliminary findings in the recent global Reef Check 1997 revealed that from the 230 sites surveyed, there was a "clear pattern of global damage to coral reefs, particularly due to overfishing and destructive fishing." How can we make a difference?
Zoos and aquariums are educating school groups, visitors and the surrounding communities about the importance of conservation which is the wise management of the limited resources and how they can make a difference. We are providing an opportunity for many to experience a world that some have never seen before, to encourage empathy with the creatures of the sea and land. So therefore, it is imperative that our displays are well designed to tell the story of an eco-system in addition to being healthy, clean and attractive.
But should we at public aquariums use live corals while we are advocating protecting and saving the reefs? I believe yes! These are the Ambassadors from the Wild. Live animals promote an emotional bond unlike preserved specimens, photographs or even movies. And it is also from home aquarists and public aquariums that we have learned how to keep corals alive outside of the sea.
One of the pioneers in the late 50ís for keeping corals was Mr. Lee Chin Eng of Indonesia. Over the years, many different systems for keeping corals have arisen.. Each combine live coral rock with good lighting and good circulation of the water. Through many experiments, corals can now grow and even be propagated in aquariums. As this is developed on a large scale, aquaculture of corals will one day eliminate the need to deplete the coral reefs to supply the demand for live corals in the commercial markets of America and Europe.
The live coral display at SeaWorld Indonesia is over 54,000 liters of saltwater circulate in a display that is two meters deep and four meters long. Nothing compares to the beauty of the live corals, beautiful fishes and intriguing critters waving in the currents, swimming amongst the rocks or creeping around the display.
Our second challenge - How to collect these corals? By carefully choosing different reefs from which to collect, corals can be individually selected. It is good to keep in mind that mild reef disturbances are conducive to coral diversity. According to Joseph Connell, it gives the slow growers an opportunity when the speedy staghorn corals are broken back in a storm.
Corals are gently broken off at their bases or taken whole if possible. Individuals are carried in plastic bags as to avoid stinging other corals as they are removed from the sea. The corals were then placed on foam in a transport tank in our boat where new water was added constantly until just outside of Jakarta where the water quality became too poor to use. If we needed to transport the corals over land, we would wrap each coral in wet newspaper and pack them within a cool styrofoam box.
Once in the aquarium, they are not an easy animal to maintain. Here is the short course! For those of you non-aquarium folks, fish give off waste products that are mostly toxic ammonia. This must be removed from the aquarium or at very low levels (0.10 mg/l), it will kill the fish. In traditional filtration, special bacteria attached to the sand grains in the filters would consume this ammonia and break it down to nitrite. A different bacteria in the filter would then consume the nitrites and excrete nitrates. Flushing the system would keep the nitrates from building up over the toxic level of 100 mg/l. This is biological filtration. So how does the live coral system differ from traditional systems?
Live Rock is needed. This is where the biological filtration takes place. What is live rock? It is the coral rock that is no longer the home of millions of polyps but to bacteria, algae and photosynthetic invertebrates. These continually take up or utilize the dissolved ammonia which comes from the waste products of the corals, fishes and other inhabitants of the tank and thus rendering it non-toxic. Other beneficial inhabitants are introduced with the live rock; brittlestars, worms and shrimp which ingest the larger particles of solid wastes, breaking it down to dissolved ammonia which is then converted by the bacteria and photosynthetic invertebrates.
The beauty of this system is that the anaerobic areas (or areas that exist without oxygen) within the live rock are close enough to nitrogenous waste produced to be immediately denitrified. To the health of live corals, even the relatively harmless nitrogenous waste nitrate (NO3) is detrimental. When it builds up in the aquarium, the normal use of it by the bacteria, algae and zooxanthellae is not as efficient. Traditional sand filters are "nitrate producing factories" and as such are detrimental if used exclusively.
Good protein skimmers are a must. These marvelous contraptions use fine air bubbled vigorously through a tower to collect the amino acids, proteins, fats, carbohydrates, phosphate, fatty acids, phenols, iodine, some metals and detritus into a brown scum which is rises to the top of the protein skimmer and is then eliminated from the system. Have you seen the foam on the beach after a forceful wave has crashed? That is the same thing - protein scum!
Good lighting. The coral derive much of their nutrients from the symbiotic dinoflagellates found within their tissues called zoothanzellae. These dinoflagellates are photosynthetic which means they use light for energy to form carbohydrates like plants do. Natural lighting is excellent but usually in aquariums, metal halides are needed to supplement the meager light derived from skylights. Itís not just the brightness of the light but rather the spectrum of light, using bulbs that emit less from the infra-red end of the spectrum and include the ultra-violet end.
Other parameters that need to be considered are the photo-period and the intensity of the light. Days are usually between ten and twelve hours in the tropics where the corals naturally occur. It is best to keep to this as animals need dark periods for some of their biological reactions. Low wattage blue lights can be used during the dark period to simulate the moonlight and can even stimulate reproduction in some corals.
The intensity of sun on a tropical reef is very high. Intensity of that magnitude is not needed in the aquarium. Depending on the corals that are in the display, one should pay close attention to the amount of light that they receive. As bulbs burn, they loose their intensity and colour temperature so they should be changed at least annually.
Wave and currents in the ocean keep the corals clean. Water movement in the aquarium is equally important. Ocellating pumps, surge machines, dump buckets, or anything that moves the water strongly will work.
Excellent Water Chemistry. This refers to the amount of ammonias, nitrites and nitrates as we discussed before but there are other parameters that must be measured and kept within range.
Temperature limits where corals are found. There are no reef building corals in water colder than 21į C. If the temperature rises above 30į C, the zooxanthellae will die and the corals slowly die, too. This is being seen in the wild where the sea temperatures have risen. The corals appear white without their colourful symbionts. This condition has been referred to as coral bleaching. Ideally, the temperature should stay within the range of 23-24į C. There is a chiller on our display as our ambient water from Jakarta Bay is already 29į C and the recirculating pumps, metal halide lamps and warm air around all add heat to the system.
pH of saltwater is usually between 8.0 and 8.4. The calcium carbonates from the coral rock is an effective buffer to keep the pH within range. Closed systems are not so lucky. That accumulating organic acids and phosphates tend to deplete the buffering capability of the system.
Alkalinity (or the buffering ability), specific gravity or how dense is saltwater compared to distilled water, phosphates, oxygen and redox or reduction-oxidation potential are all important aspects that must be monitored and adjusted.
As the primary building block of corals, clams and calcareous algae, calcium is very important. It is normally found at a concentration of about 400 mg/l in saltwater but near coral reefs it may be higher at 425- 480 mg/l. In the ideal aquarium, it should be maintained near 500 mg/l. The market is flourishing with calcium supplements but all have not been thoroughly tested. One effective means to raise the calcium levels is to use calcareous water or kalkwasser (limewater). It is made by using water that was purified by reverse osmosis and or deionization. Plant nutrients normally found in tap water are thus eliminated. To one litre of purified water, an excess of 1.5 g of calcium hydroxide or calcium oxide are added. This needs vigorous stirring as it tends settle out and then set aside for an hour. The clear, saturated liquid is the kalkwasser and is added whenever water changes are done. Considerable care must be taken when adding this as the pH is 12 and if too much is added at once will shock the corals and inhabitants of the display.
Strontium is only a minor element in the make-up of water but it is incorporated in many organismsí skeletons. It is one of the key ingredients needed for the growth and survival of corals in the aquarium. Strontium is a hazardous chemical and should be handled with care. Solutions of strontium can be made and added to the aquarium little at a time.
Trace elements can be added using commercially available solutions and should not be neglected.
So that is the short course for Coral Reef Aquarium keeping. But we must always keep in mind why we are keeping miniature coral reefs in aquariums. Our biggest challenge is to educate our visitors in an effective manner that is also entertaining. Readable, understandable graphics and informed education staff available for those guests that are motivated to know more. High quality displays that tell a story about an eco-system, about an unusual lifestyle or an endangered species are a must. Exhibits that encourage captive breeding and the experimentation and study needed to support wise management of the animals within our care. Anything less and we will loose our credibility. These children we influence are important; they will be the future policy holders of tomorrow.