The landscape of a reef aquarium is not merely one to engage the senses, although aesthetic function is certainly important to the tank keeper. Aquascaping in reef aquaria is primarily based around the structure of live rock and often sand substrate. In the past, it was suggested that up to 2 pounds of live rock per gallon of tank water capacity be used to provide adequate filtration. Over the years, however, and depending on the weight and shape of live rock, it has become apparent that the earlier estimate was exaggerated. Not only are lesser amounts of live rock capable of managing biological and mechanical filtration of substantial bioloads, but, in this case, less is actually more.
Reef aquaria in the past, as well as many “older” style aquaria currently in operation, consisted of large massive walls of live rock, occupying virtually every square inch of the aquarium. As such, it was difficult to obtain a “natural” look, much less function. Typically, such aquaria were soon filled with undesirable filamentous algae, large pockets of detritus and waste material, and occasional populations of corals and invertebrates wedged into nooks between the calcareous boulders. Invariably, coralline algae and various other photosynthetic organisms could not thrive except on the surfaces actually exposed to light. Similarly, the numbers of corals and other light-seeking invertebrates were limited as to the availability of space occupied by so much rockwork.
There are other difficulties with such massive and cumbersome aquascaping protocol. Perhaps foremost is the compromise in water movement and circulation patterns within the captive reef. With the exception of deep water and cave dwelling organisms, most of the sessile and motile life on a reef is exposed to great amounts of water displacement. Even those lifeforms that dwell in relatively calm lagoon areas, while not always exposed to strong or fast currents or wave action, are treated to relatively short water dwell times; by this I mean that even calm lagoons are exposed to massive water flux, washing, and dilution through the water volume itself, waves, tides, and currents. Reef organisms depend greatly on the flushing of their habitat to remove wastes and provide food and gas exchange. Without it, biodiversity and success wanes. Reef aquaria are even more dependent on adequate flow that wild communities, partly because of the lack of water volume and the general lack of food (though not water quality degrading dissolved nutrients) that only compound the problems inherent to captive systems.
A reef aquarium today, barring the desire to create specific niche environments, should be a more sparse landscape of hard substrate (live rock). Open architecture consisting of various pillars, mounds, buttresses, channels and caves provide a more natural framework for the organisms generally kept in such tanks. Water flow can circulate in and around such formations unimpeded, providing the very important water flow that contributes to the health of the inhabitants, including fish, corals, sponges, and invertebrates. The opened architecture allows for better coralline algae growth, exposes more surfaces to light, and allows for more numerous, accurate, and beneficial placements of corals and sessile invertebrates. It is important to remember that corals, sponges, and many other filter feeding invertebrates are also highly efficient water filters and purifiers. They contribute to, as well as depend on, high quality water. Live rock, excepting the biodiversity and waste processing abilities of various small organisms and bacteria living within the interstices and pore spaces of rock, is a mostly passive substrate. Corals and other filter feeders, in contrast, actively remove organic material such as dissolved nutrients and detritus from the water as a food source. They also harbor large populations of productive bacteria on their surfaces that further contribute to heightened water quality. In total, open architecture contributes to a vastly more successful and productive community and reef aquarium. As such, it is more functional, more natural, more attractive, and—as an added bonus—less expensive.
On the other end of the spectrum are specialized niche habitats. These aquaria are based on the replication of smaller or specialized area of a reef or reef-associated area. As examples, mangroves, seagrass beds, sand flats, caves, or even tanks centered around a few organisms (i.e. a stand of Acropora or a large anemone) are subject to their own set of rules. These niche-type habitats should be encouraged as closed water volumes often stocked with animals that eventually grow much larger than the aquarium are more natural replicates of the natural environment and, often, are also more successful as unnatural pairings resulting in competition are minimized and appropriate habitat maximized. Each of the examples above has a plethora of available organisms to create a realistic aquascape and maintain a healthy environment for its inhabitants. The costs may also be much less, depending on the habitat that is designed. Such habitats should be planned in advance and carefully designed and researched to determine the nature and types of organisms that would ordinarily be found in such environments. I also feel that reproductive behavior might be more likely than in “garden tanks” where every type of reef species is forced to occupy the same, and often very unnatural, confined space.
Public aquaria have recognized the benefits of such niche displays for decades, and while the aquarist may see limitation in their ability to stock all the species they desire, the niche tank can often be done on a smaller scale, and perhaps multiple tanks rather than one large tank will satisfy such desires in a more productive, natural and effective manner. In my own case, I have connected such individual habitat tanks together, separating them by spatial dividers while maintaining a common water column.
Whatever the solution, the individual needs of the aquarist should be carefully considered, and the habitat designed around those needs. It is far more attractive and desirable to “build” the aquascape to mimic the natural environment and then introduce the appropriate species that simply to buy a tank and equipment and then begin stocking it by throwing in any species that has aesthetic appeal.
Eric Borneman is the author of Aquarium Corals.