i call systems featuring a trickle or wet/dry filter Dutch-style aquariums, and there is no doubt that these relatively complex setups ushered in a revolution in marine husbandry. The introduction by Dutch proponent George Smit of the "wet/dry" filter, adapted from wastewater treatment technology, resulted in a new wave of interest in minireef aquarium keeping. This new filter system was much more efficient than the undergravel filter and bypassed many of the former system's drawbacks (Smit, 1986a, 1986b). The filter media, kept wet but elevated above the water level of a sump, could support large populations of nitrifying bacteria that seldom or never had to be disturbed by cleaning sessions. The trickling flow of water provided an excellent situation for gas exchange and oxygenation of the system water. The Dutch method also relied largely upon fluorescent lamps as a light source and frequently employed additional techniques, such as ozonization, to cope with organic matter.
Unfortunately, wet/dry filter systems relied on exactly the same biological approach as the old undergravel models: mineralization of nitrogenous wastes through bacterial activity. This eliminates problems with ammonia toxicity, but creates a new set of problems related to accumulation of nitrate and reduction of pH due to the generation of hydrogen ions. Fish are not particularly sensitive to nitrate, even in high concentrations, and their osmoregulatory systems can function over a range of pH. As long as marine aquariums were constructed of artificial materials and stocked only with an appropriate assortment of fishes, water chemistry resulting from biological activity could be satisfactorily maintained with an undergravel filter and a program of regular partial water changes. When invertebrates and seaweeds were included, however, only the hardiest species — hermit crabs, sea urchins, and predatory starfish, to name some popular examples — could survive for long, unless the system was built along the lines described by Smit. His success was attributed to the supposed improvements embodied by the wet/dry filter. Smit's aquariums were beautiful displays of invertebrates, with much live rock and abundant macroalgae growth. Owing to the presence of these important factors, they sustained diverse communities of organisms, perhaps despite their utilization of the wet/dry system.
Smit's original designs were marketed in the United States by International Seaboard, in Cicero, Illinois. In 1987, my partner, J.R. Shute, and I made the eight-hour trek to Chicago to visit the factory and see Smit's aquariums for ourselves. We had just begun a tiny business called Aquatic Specialists and were interested in bringing this
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