The “Closed Equilibrated Biological Aquatic System” (C.E.B.A.S.) is originally dedicated to long-term multi-generation experiments with aquatic organisms in a space station (a national German option for the COLUMBUS module). The development of the laboratory prototype and the results of the international multidisriplinary zoological frame program was frequently presented at most space-relevant congresses and symposia since 1989. It consists of 3 components: 1. an aquatic animal tank with water recycling system (ZOOLOGICAL COMPONENT), 2. an aquatic higher plant chamber or microalgal bioreactor (BOTANICAL COMPONENT) and 3. a process control system (ELECTRONICAL COMPONENT). This system has a volume of approx. 100 liters was already successfully mid-term tested in its second and optimized version in which the BOTANICAL COMPONENT was filled with a rootless higher water plant. In addition, for spacelab or biosattelite experiments a MINI MODULE of the C.E.B.A.S. system fitting into a spacelab middeck locker tray was developed and tested in parallel the second version of which exhibited a biological stability between fishes, higher water plants and microorganisms of more than 40 days as reported on the World Space Congress in 1992. In the same year a third and highly optimized version of the C.E.B.A.S.-MINI MODULE was elaborated and tested from december 1992 until march 1993. As its precursors it has a total volume of about 11 liters and consists of the following subcomponents: main animal tank, bacteria filter, coarse filter, plant chamber and second “small animal” chamber. The water is driven through the system by a rotatory pump, the main animal tank and the plant chamber are illuminated by 4 W fluorescent lamps (adjustable for the latter). For emergency cases, a gas exchanger is inactively positioned in a closed side loop. A simple data acquisition is permanently monitoring pH-value, redox potential, pressure, temperature and oxygen saturation.
During the experiment all relevant ions and the water hardness were determined chemically in daily intervals. The photoperiod of the main animal tank was 12 : 12 hours the plants were permanently illuminated. The agreed experimental animals of the international C.E.B.A.S. scientific frame program were utilized: the ovopviviparous teleost fish species