The Natural Aquarium
From Microcosm Aquarium Explorer
Introduction
Excerpt from: Natural Reef Aquariums
The “Natural” Aquarium
A Personal Journey and a New Approach to Captive Reef Keeping
By John H. Tullock
The hustle and glare of Miami faded quickly behind us. We were headed south, beyond the reach of the Florida Turnpike, stopping only briefly in the farming town of Florida City for gas and produce. I marveled that the tomatoes, vine ripe in early May, tasted no better than those trucked to the grocery shelves back home in Tennessee.
Rolling south on A1A, we crossed the bridge over Card Sound and were in the Keys. Dense tangles of mangroves edged the road, osprey nests perched on the tops of telephone poles, the ocean was visible on either side of us. We were barely two miles from the mainland and life was different already.
The Florida Keys stretch from Biscayne Bay, curving south and west nearly 400 miles to terminate in the uninhabited Dry Tortugas. About midway along this thread of coral rock outcrops — with the Gulf of Mexico on our right and the Atlantic Ocean barely 50 yards to our left — lies the old Seven Mile Bridge. This motorway bridge, built on the trestle after the original railroad bridge was destroyed in the great hurricane of 1935, spans the broad, shallow channel that separates the Upper and Lower Keys. At the northern end is the town of Marathon; to the south lies Big Pine Key. And smack under the middle of the Seven Mile Bridge is Pigeon Key. This dot, scarcely two acres in size, held our destination, the University of Miami marine laboratory.
The Lessons of Pigeon Key
The dozen or so white clapboard buildings scattered about the island had been constructed as barracks for the crew that built the railroad in the early 1900s. I arrived there that day in 1977 with 20 other students, a couple of graduate assistants, and Dr. Sue Reichert, Professor of Zoology at the University of Tennessee. The course was Invertebrate Zoology. I hardly suspected that my dormant fascination with the sea and its creatures would waken to shape my future. The expanse of coral rock dotted with Australian pines, with the sea visible from every direction, held for me then nothing more exciting than the anticipated week of field work requisite for completion of the course.
Our accommodations could charitably be called “basic.” The barracks, built of whitewashed wood and elevated a few feet off the coral rubble, had a porch at each end. Bedrooms with military-style cots and bunk beds flanked the central hallway. Bathroom facilities were unisex. My colleagues and I avoided most difficulties that might have arisen from these arrangements by showering in two shifts, according to gender. Other minor details of coed living were dealt with by signs left there by generations of students before us. Identical 3x5 cards above each sink said, “Rinse sink or don’t shave.” The door to the water closet was marked in capital letters on the peeling paint: “KNOCK FIRST, DAMN IT!” Another sign was posted in the hallway by the back door of our barracks, next to the pay phone: “On July 12, 1857, this structure received the distinction of being the first building in North America to be condemned.”
The ramshackle nature of Pigeon Key’s fading physical plant enhanced the feeling that the Keys were a rustic wilderness not yet invaded by the hordes of tourists that thronged to Orlando and Miami. This string of islands, thrusting out from the tip of the Florida peninsula like a giant sense organ extended to sample the warm waters to the south, is as rich in history as it is in subtropical flora and fauna. Pirates, gunrunners, and dope smugglers, who in succession had plied the Straits of Florida, all had left their marks on the local culture. There were seedy little taverns near the docks in Marathon full of old sailors: brown leather faces, gray stubble, and endless talk of Cuba or fishing or how America had gone to hell since Ike left office.
On my first night at Pigeon Key, I wandered alone down to the Gulf side with a flashlight. Wading out into the warm, virtually motionless water, I played the light back and forth across the bottom, anticipating nothing in particular. The clear water and pale-colored coral rock on the floor of the lagoon made visibility perfect. Brittle stars slithered away from the light, quintets of arm-legs flailing like Marine recruits belly-crawling under barbed wire and live fire. Eyes shone back at me from dark recesses. Snapping shrimps fired warning shots, audible even above the surface. And in a patch of Caulerpa, the largest sea slug I had ever seen undulated along. It was too busy eating seaweed to take notice of the terrestrial creature in tennis shoes towering above it. It was a sea hare, Aplysia, a close relative of the sea slug Tridachia. To find such a fascinating creature at the water’s edge, almost without a search, crystallized my desire to make this path of graduate study successful. I resolved, standing there in the Gulf of Mexico in the middle of the night, that this warm, shallow sea would give up at least a few of its secrets to my inquisitions.
Thinking I would take this first discovery up to the lab and put it in one of the water tables for closer observation, I scooped up the sea hare in my right hand. At once, a lurid shade of purple ink emerged from its body, trickled between my fingers, and ran down my arm and onto my swim trunks. Startled, I dropped the creature into the sea. The secretion, I later learned, is thought to create an olfactory smoke screen to thwart the efforts of predators who hunt the sea hare by smell at night. At the time, for all I knew it would raise blisters on my skin. Fearing the worst, I splashed around frantically, trying to wash the ink away. At length, satisfied that the purple dye was harmless, I mused that this response from the sea hare had been quite effective in deterring me from interrupting its evening meal. The ink, which had for millions of years protected generations of sea hares from predators, would perhaps protect it from the ultimate predator — man.
Soaking wet, I waded back to shore and headed for the lab. Over the water table was another of Pigeon Key’s ubiquitous signs: “No Aplysia in water table. Ink gums up filters.” I had so much to learn.
The days and nights spent snorkeling, wading, and collecting marine life in the waters around Pigeon Key rewarded me repeatedly with new insights about the marine environment. For one, it was apparent that even as small an outcrop as Pigeon Key was encircled by distinct ecological zones. Marine organisms from one area were seldom found in the other. I would go out into the ocean and collect specimens from a certain spot until I had filled two buckets, returning to the lab to empty the contents into their own aquarium or water table. I soon began attempting to arrange each aquarium to mimic what I had seen in the ocean just beyond the door. It wasn’t long before it occurred to me to try to take home one of these collections and rework my marine aquarium to reflect what I had seen at Pigeon Key.
My First "Reef Tank"
Like other aquarium hobbyists in the ’70s, my marine tank consisted of dead bleached coral skeletons and large, showy fish. Its main attraction was “Sultan,” a Volitans Lionfish that had rapidly grown from a 2-inch baby to a foot-long eating machine and who demonstrated no inclination toward a slowing of its growth rate. Partly because the food bill for this fish was beginning to tax my meager stipend from the university, I gave him to a dentist who had a much bigger tank and presumably a better income. Sultan was replaced by a collection of invertebrates, macroalgae, and rocks collected in the Keys. Over the next ten years, I would make many more visits to Pigeon Key. Each time, I came back with new specimens and new ideas for my aquarium. Looking back, I consider this to have been my first “reef tank,” because the goal of its design was to duplicate the natural habitat I had observed in Florida.
A reef tank is a display of tropical marine invertebrates and, often, fishes that approximates the appearance of a small section of natural coral reef habitat. It is arranged according to its creator’s intent to achieve an aesthetically pleasing effect, and its development and management involve both art and science. I will try to provide the science in the chapters on technique that follow.
To create art, however, requires an understanding of the reef environment on a level that goes beyond the technical specifications for the life-support system. The art expressed by a reef tank, like that of a Japanese tea garden, results from the juxtaposition of living and nonliving elements in an arrangement that imitates nature, but fits into an unnaturally small space. When the gardener is successful, the observer is unaware of the confinement, and the view seems as encompassing as a mountain vista. Similarly, aquariums are not real ecosystems; by definition an aquarium is an artificial creation. Yet when thoughtfully executed by an aquarist mindful of ecological relationships, a reef tank deceives the eye into believing it is looking through a window to the sea, teeming with life and awash in color and flowing movement.
Unfortunately, marine aquariums, even large public displays created at great expense, are often anything but naturalistic. Big fishes, displayed in population densities that test the limits of elaborate filtration systems, against a backdrop of bleached coral and uniform, shiny white gravel, are still around, indeed are often showcased, in hotel lobbies and doctors’ waiting rooms. Such aquariums no more resemble a coral reef habitat than a florist’s arrangement of Anthuriums resembles a Hawaiian rain forest. Sometimes, especially in public aquariums, an effort is made to make the exhibit appear more “natural” by replacing dead coral skeletons with plastic reproductions dyed to approximate, with varying degrees of success, the colors of living corals.
In fairness, I acknowledge that a few public aquariums are beginning to craft exhibits with living invertebrates and seaweeds. Dr. Bruce Carlson’s stony coral exhibits at the Waikiki Aquarium come to mind, and a similar exhibit for the National Aquarium in Baltimore is planned. Though impressive from the standpoint of sheer size, the best efforts of most public aquariums — if the goal is to create a visually appealing display that reflects some aspect of reef ecology — are easily outdone by the majority of home hobbyists whose reef tanks I have observed.
Perhaps the benefits of the natural approach to aquarium keeping will be revealed to the public aquarium community as successful exhibits, such as those at Waikiki and Baltimore, are discussed at scientific meetings and in the literature. Given that one benefit of the natural approach can be significant maintenance-cost savings, when compared to traditional methods, these natural techniques may continue to win converts.
Philosophy of the “Natural” Aquarium
My approach to keeping marine organisms in captivity emphasizes the duplication of nature in as many details as possible. First and foremost, providing a physical and chemical environment closely similar to that found in nature is essential if coral reef organisms are to remain alive for any length of time. In this sense, any aquarium must duplicate nature to a certain degree. My methods attempt to go further than this, seeking to duplicate the biological environment found on a real coral reef. This might at first seem like a difficult task, but it can actually be done rather easily, if one will pay attention to what is known about the biology of the organisms that inhabit the aquarium.
The existence of coral reefs has been known for centuries, but not until the development of scuba diving methods did we really begin to learn very much about them and the organisms they harbor.
Reefs develop only in areas of the ocean where specific conditions prevail. Light, in particular, must reach the coral organisms, because all reef-building corals harbor photosynthetic, symbiotic algae. Thus reefs form only where water clarity is sufficient to allow adequate light penetration. Sediments, usually transported from the coastline by rivers, not only reduce light penetration but also can smother and destroy coral growths. Clear, sediment-free water is the primary geological requirement for the development of coral reefs. To a lesser extent, salinity, temperature, the availability of nutrients, water movement, and underwater topography all play a role.
Reefs have developed, generally speaking, only in the Tropics, because of optimal temperatures, and primarily on the eastern coasts of the continents, because of the effects of prevailing currents on water temperature and clarity.
While the geographic distribution of reefs is due mostly to local physical conditions, the biological structure of the reef ecosystem is the result of factors that students of the reef have only begun to elucidate.
As the noted coral biologist J.E.N. Veron has explained: “This diversity can only exist after a series of ecological balances is achieved: not only balances between the corals themselves, but between the corals and other organisms, including predators and parasites, and also between other organisms that have little to do with corals directly, such as the balance between herbivorous fish and macroalgae (the latter would rapidly overgrow most coral communities if it were not continually held in check).
“As far as the corals themselves are concerned, each species has its own array of growth strategies, food requirements, and reproductive capacities. Each has its own response to disruption by storms or predators, diseases and plagues. Each species competes with others for space, light, and other resources. The net result of all these interactions and balances . . . is to make coral communities among the most diverse of any communities on earth.”
Understanding that such a complex web of ecological interactions exists on the reef helps to explain why specific conditions have to be met in the aquarium before reef species will survive. Many of the species of marine invertebrates that are offered for sale in aquarium shops do not actually come from coral reefs proper. Some species, such as Open Brain Coral (Trachyphyllia geoffroyi), occur shoreward of the reef in the quieter, more nutrient-laden waters of the lagoon. Tolerant species like this can be included in an aquarium designed to duplicate that inshore habitat.
We must accept the fact that we cannot recreate the ocean in our living rooms. The best we can hope for is a representation, a display of species that are characteristic of a tiny portion of the ocean realm — a microhabitat. Creating a microhabitat display for invertebrates is a project with a higher chance of success than doing the same for most fishes. This is because fishes move around, and habitat types overlap, while invertebrates by and large remain fixed in place and often occupy a rather limited range of habitat types.
There are three major features of my approach to keeping “microhabitat displays” of tropical shallow-water invertebrate species.
The first of these I will call “less technology, more biology.” The husbandry of marine life must be performed in light of the specific ecological needs of the species of interest. Granted, system design cannot be overlooked, but one must begin the thinking process about any aquarium by asking questions about the needs of the species that will occupy it. This principle is easily illustrated. An understanding that most tropical cnidarians (formerly known as coelenterates) require intense, wide-spectrum lighting as an energy source for their symbiotic zooxanthellae made it possible to keep these species alive in aquariums. In the past, hobbyists were told that anemones, for example, needed everything from carbon filtration to trace element supplements to survive, when what they actually were missing in the aquarium environment was appropriate light.
One of my favorite analogies is the comparison between a tankful of marine invertebrates and a flower box full of terrestrial plants. I am an avid gardener. Those familiar with gardening literature know that when one opens the pages of Horticulture or National Gardening one is not likely to see articles about the latest advances in the design of rototillers or greenhouse heaters. What one finds is articles about plants. The priority in gardening is responsiveness to the needs of the plants, not the needs of the gardener. More of this kind of thinking would benefit the aquarium hobby.
Reef tanks established by the “natural” methods outlined in this book are the most successful, easiest to maintain, and most likely to provide what species need to complete their life cycles. The common features of such aquariums are:
- ample quantities of “live rock” and “live sand”;
- high-intensity, broad-spectrum lighting;
- filtration equipment that focuses on removal of organic wastes rather than mineralization of them;
- husbandry efforts focused upon limiting quantities of inorganic nutrient ions, while insuring a supply of other inorganic ions in concentrations that match or exceed those found in the ocean;
- replication of the physical characteristics of the microhabitat, in terms of substrate type, current patterns, diel cycles, and temperature; and
- attention to the specific community relationships of the species housed together in the same aquarium. In other words, one must try to copy Mother Nature.
Not all technology is undesirable, of course. One would be foolish to reject it entirely. The challenge is to learn to apply the required technology with finesse. One of the best new advances is in the area of more accurate measurements of the aquarium’s physical and chemical parameters. Electronic meters have begun to supplant color-change test kits for the measurement of pH, for example, because such instruments are faster, more accurate, and easier to read. This is an example of an appropriate application of technology to aquarium management.
On the other hand, one cannot reduce the dynamics of an ecosystem, even the small and relatively uncomplicated ecosystem of an aquarium, to a table of numerical parameters. The aquarist who nods in satisfaction at a correct pH reading or a high redox potential, yet fails to heed the message conveyed by a disintegrating gorgonian or a Xenia that has stopped its rhythmic pulsations, is missing the point altogether. The natural approach requires you to become an observer of nature, not of digital readouts.
The result will be an aquarium that is realistic, with healthier, more colorful animals that survive better than their counterparts in traditional tanks. In addition, the abandonment of technical props that were once thought to be essential components of the “filtration system” can result in significant cost savings.
By following the natural approach, one can dispense with wet/dry filters, ultraviolet sterilizers, ozonizers and redox controllers, reaction chambers, artificial media to remove nitrate, phosphate, silicate, and other ions, denitrators, and a host of other expensive paraphernalia. The equipment one does require — lighting, pumps, protein skimmers — is uncomplicated in design and straightforward to operate. The essential biological elements — live rock and live sand — are interesting in their own right and add to the aquarium a touch of realism that artificial decorations or the skeletons of dead corals cannot convey.
Biology & Amateur Science
The second major feature of the natural approach is reliance upon an understanding of biology. The ecological relationships among species and between individuals and their habitats are most easily expressed in the terminology of biology. The language of science lends great precision to discussions and helps to make sense of the bewildering diversity of marine life and marine habitats. I was educated as a scientist, and I will use many scientific terms in the pages that follow. I have attempted to explain unfamiliar terms where appropriate.
Having said all this, I nevertheless agree with Stephen Spotte’s assertion (1992): “Science alone has little practical application, and works dealing strictly with technology omit information necessary to foster understanding.” Maintaining reef aquarium displays owes much to the application of science. However, we must not ignore the importance of circumstantial or anecdotal information concerning organisms and their behavior in the aquarium.
Most of these observations will have been made by nonscientists, but this does not imply that the information is not useful to those who desire to own a reef aquarium and who hope to profit from the experience of others. One should never be too quick to accept the testimony of observers as gospel. On the other hand, these observations, if carefully made and offered up with an honest intent to convey helpful information, are every bit as useful as those of professional scientists.
I feel strongly that amateur aquarists have important contributions to make concerning mankind’s knowledge of the intricacies of coral reef ecology, and that the efforts of dedicated hobbyists should be encouraged by professional marine biologists. Aquarists who share this view must make an effort to learn the lingo, however. The reward for this effort is freedom from the depredations of gimmick promoters and snake-oil salesmen who sometimes enrich themselves at the expense of the hobbyist. Access to information is the surest defense against useless products and false claims.
The Reef Tank As Teaching Tool
The last feature of my approach is perhaps the most important one to the future of our hobby. The development of techniques for keeping an ever-widening variety of marine life in home aquariums has fostered an awareness of the marvelous richness, diversity, and beauty of the marine realm, even among those who are not themselves aquarium owners. Reef tanks are often displayed prominently, in the living room, for instance, in their owner’s homes. As a result, large numbers of “ordinary” people — friends and relatives of the aquarist, primarily — have the opportunity to examine, say, a Tridacna maxima giant clam face-to-face.
Without aquariums, the vast majority of people would never see coral reefs up close, except on television. In their quest for large audiences, television producers spend a lot of time and videotape on sharks and other large, spectacular sea creatures. Rarely does television present us with the delicate beauty of an anemone or allow us to glimpse the daily life of the cleaning shrimp that lives among the anemone’s tentacles. Naturally, being able to experience reef creatures in a way that not even the best television documentary can duplicate influences how people who view reef aquariums think about coral reefs. This awareness, in turn, increases the desire to see reef resources preserved and protected.
I see some interesting parallels between reef aquarists, divers, and other nature enthusiasts of today with their counterparts of a hundred years ago. Nature study was a popular pastime among our Victorian ancestors. The microscope was their primary tool for investigating the natural world. The structure of an organism, in that it was considered to reflect the precise, clockworklike design of a Divine Plan, was their primary interest.
Today, the aquarium has become a tool that permits even an urban apartment dweller to investigate nature. A reef tank is as affordable for many Americans as a good microscope was for Victorian ladies and gentlemen. We, however, are less interested in how organisms are constructed than in their relationships with each other.
When we create these miniature worlds encased in glass or acrylic, we are not seeking to affirm the presence of a greater power (although such affirmation is a commonplace reaction of spiritually inclined aquarists). Rather, by observing the day-to-day existence and interactions of creatures that are like us in so many ways, and yet so startlingly different, we are attempting to comprehend our place in a universe that is proving to be more chaotic, complex, and awe-inspiring than anything the Victorians could ever have imagined.
Excerpt from: Natural Reef Aquariums