In the late 1950s and early 60s Lee Chin Eng, an aquarist who lived in Indonesia, reported great success with a method of aquarium keeping that he called "nature s system" (Eng, 1961). Mr. Eng used unfiltered seawater, and circulation in his aquariums was achieved with air bubblers within the tank, either airstones or open ended air hoses for larger bubbles. The aquarium decor consisted of live rocks with attached plants and invertebrates, and live corals. His technique, now called the "natural system" or "Lee Chin Eng method", did not receive much acceptance at the time since it was believed to depend on too delicate a balance to succeed. It was believed that since there was "no filter" in these aquariums, they could not support a very high population of fish.
Furthermore, many aquarists who attempted to duplicate this system at home met with failure and a smelly mess. They published such results in aquarium literature, which effectively discredited Eng's methods and reputation. The reason for their failures is plain to see now for aquarists familiar with modern "living reef aquaria": the fresh live rock fouled, and these aquarists did not know enough, or were not patient enough to allow the rocks to become seeded for several weeks before adding fish or invertebrate specimens. We now knowr that biological filtration in these systems occurs within the live rocks, where nitrification and denitrification proceed side by side, and that these systems are not fragile or unstable. We know this because Eng's method does not differ much from our "modern" techniques.
The Berlin method of aquarium keeping employs natural system philosophy, combined with the additional benefits of protein skimming, and calcium and trace element additions. Eng used natural sunlight supplemented with fluorescent tubes, while Berlin methodology uses metal halide lights with supplemental blue fluorescent light. Eng lived by the sea and could change water to replenish depleted trace elements and calcium, though he reported success without regular water changes (Eng, 1961). In addition, vigorous aeration by means of airstones within the aquarium, as Eng practiced, does achieve some protein skimming. Tins can be witnessed along the aquarium walls just above the water line.
Natural system aquaria are both simple and inexpensive to create and maintain. To avoid the failures initially encountered with this
Figure 5.4 Natural Systems
Berlin System Makeup
Dr. Alley's System
Wave -Surge Bucket
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Coral Sand (Aragon ite)
Dr. Jaubert's System
Lower Sand Layer
Lee Chin Eng's System
Live Rock Coral Sand
method, one must start by using cured or seeded live rock. See the sections "Methods for Establishing Reef Aquaria'" and "Establishing an Aquarium Without a Trickle Filter \ in this chapter.
As with other systems for maintaining reef ecosystems, one must not overlook the importance of water motion. One airstone in the aquarium may keep it alive by providing sufficient gas exchange for survival of the organisms, but to make the captive ecosystem thrive, the water must really move. It is quite a surprise for aquarists familiar only with centrifugal pumps for moving wrater, to see how efficiently rising air bubbles create substantial currents throughout the aquarium. In addition, the size of the bubbles dramaticallv affects the manner in which the water motion is j generated, and the velocity of the resulting currents. Smaller bubbles set up laminar current flow similar to that generated by pumps. Larger bubbles generate turbulence, and really big bubbles create small waves! In a description of one of Eng's aquariums in the lobby of a hotel in Indonesia, "large flat bubbles" were seen percolating up from beneath large rocks (Emmens, 1975). Eng clearly recognized that larger bubbles made the entire volume of water oscillate; an efficient means of achieving water motion o throughout the tank. His critics probably didn't understand the importance of this simple application.
In an air conditioned or naturally cool room with good sun exposure, artificial illumination is not necessary, and the aquarium can be placed near a window. Most aquaria will require supplemental illumination, however. Smaller aquaria must be observed carefully since they can rapidly change temperature, depending on exposure to the sun. A heater may be necessary as well to prevent wide temperature fluctuation from day to night in a cold climate.
A lid over the aquarium is essential to slow evaporation and prevent the settlement of dust on the surface. These features can also be managed by means of surface skimming and level switches with automatic water make-up, but those techniques we reserve for Berlin methodology and, though they are not complicated, we wish to emphasize the simplicity of the natural system and keep its definition intact.
Nevertheless, some additions to the purest form of this method do afford better results, and merit recognition here. For example, the placement of a bag of activated carbon beneath an easily moved
live rock adjacent to the circulation from an airstone will maintain the water colorless. Although this is not the most efficient means of employing activated carbon, it achieves the principal desired effect of colorless water without rapidly depleting trace elements. The carbon may be left unattended until the water becomes noticeably colored, usually after about six months.
Mr. Eng died in the early 1980s shortly after he moved from Indonesia to Australia. His input surely would have made an impact during the rapid development of the reef aquarium hobby in the USA and Australia, which occurred not long after his death. We don t know if he was aware of the hobby in Europe that developed while he was still living. He might have been flattered to learn that the most successful techniques developed in Europe in the late 1970s and early 1980s were based on his methods.
A version of Engs system has been developed and studied by Dr. Jean M. Jaubert at the University of Nice, France. Jaubert has set up several exhibits, ranging in size from 1 to 40 m\ No external biological trickle filters, activated carbon, or foam fractionators are used. Circulation is from large airstones and water pumps. No water changes are performed for some systems, though some at the Aquarium in Monaco receive 5% per month water changes. The system employs a unique form of biological filtration (French patent number 03 28474, U.S. patent number 4,995,980) within the aquarium, or in separate connected reactor tanks (Jaubert, 1991). A perforated false bottom partition is used, similar to an undergravel filter plate, under which a body of confined water exists. A thick layer of coral sand and gravel lies on top of this partition, retained by screens to prevent fish or other marinelife from disturbing its uniform thickness. Another layer of sand covers the screen
(Jaubert, 1991). The aquarium (or reactor) is heavily illuminated to encourage the growth of photosynthetic corals, anemones, and algae. This maintains supersaturation of oxygen during the day above the sand, and low oxygen content in the confined water below the plate. Aerobic nitrifying bacteria and algae colonize the upper layer of sand, heterotrophic denitrifying bacteria exist in the lower layer, and an intermediate region between them has a mix of aerobic and anaerobic organisms (Jaubert, 1989, 1991). The confined water space maintains permanent stratification of aerobic and anaerobic layers in the sand. Movement of oxygen, ammonium, nitrite, nitrate, nitrogen, and carbon dioxide through the substrate occurs by diffusion (Jaubert, 1989). Reactor tanks that can be used as accessory biological filters for any aquarium may
have vertical partitioned chambers, using screening to retain the sand and gravel, or may simply use a fibrous matting material
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