AQUA 2East3 is one of five units, at these coordinates, dedicated to the breeding, production and processing of Tilapia Niloticus (Oreochromis), a fish wellsuited to breeding in captivity. Tilapia has been cultivated as a farmed fish over a period going back to Egyptian times. Its name means fish of the Nile. It is widely cultivated on Earth across many cultures. It would certainly be an admirable partner in any outward exploration into space, adding tasty variety to the daily diet. This fish has the advantage of being self-sustaining as a source of food.

Although there are economies in scale in creating larger single facilities, the vulnerability of such, and reliance on this farming as a source of nourishment, dictates that units are spread out in small clusters to avoid any single event from wiping out all production at once. Accidents, meteorites, fire, or technical failure (including computer crashes or power cuts), could leave colonists without any seed-stock to reboot fish production, if literally, all eggs were in one basket.

This is a semi-automatic unit, requiring only low supervision and is not staffed full-time. Computer control of heating, water purity and oxygenation, feeding and waste removal and monitoring of average fish growth, all are reported to a central control. Each unit has its own CPU, with backup power systems, and stores of air and water. Routine visits to supervise movement of fish from spawning to fattening tanks, and harvesting, occur at regular intervals. Food pellets are top-loaded manually into the individual gantry hoppers, but timed feeding cycles are under electronic control. It is important that all organic material goes straight into the tank. Forgotten decomposing residues cannot be permitted to build up anywhere in the delivery system, such as might happen in a long chain mechanical transport method, as they could give rise to health hazards in such a sealed environment. This could affect both fish and personnel.

Stock tanks are formed from a series of horizontal circular sections, assembled on site, that are fastened together at flanges with O-ring seals, pressure from the vertical ribs clamping them together to maintain watertight integrity. Individual sections can be replaced easily, or tanks cannibalised to repair other units, so maintaining production with minimum interruption. Although much of the working medium (water) is recycled within each aquaculture centre, some input is taken through the central tunnel pipelines of energy, water and air. Background heating is supplied conventionally, piped from the basement to radiators, but the warmth of the stock tanks maintains most of the units ambient temperature. Water is circulated continuously through each culture tank, providing an input of clean liquid from above that has been filtered, warmed and oxygenated from the basement chambers processing systems. Solid wastes are drawn from the base of the tank, and reduced to a low moisture content solid that is further dehydrated before being used as powdered fertiliser in greenhouses. This may also be linked directly as an outgoing fluid flow to fertilise chlorella farms. Waste from processed fish: bones, heads, scales etc. can be used as horticultural fertiliser after open atmospheric dehydration and sterilisation.

Tilapia can be broiled, fried, grilled, baked, poached, sauteed, or steamed. It has a mild, sweet, flavour. The fish can be harvested on a year-round basis, and fed from a variety of sources: processed kitchen and horticultural waste, food pellets, chlorella by-products and waste trimmings, or tankbred yeasts or planktons. It can be frozen, and stored in this form for up to six months, providing a buffered food source in times of any other shortfalls. A good source of protein, not containing potentially damaging saturated fats, particularly important in a potentially more sedentary planetary gravity.

Nutrition (per 100g raw weight) Calories: 98, Fat Calories: 22, Total Fat: 2.4g, Saturated Fat: 0g, Cholesterol: 0g, Sodium: 52mg, Potassium: 0g, Protein: 18.5g, Iron: 0g.

Tilapia are copious breeders: a growth record recently achieved has been fourteen fish generating up to 14,000 offspring in just two and a half months. Careful selection and monosex segregation has to be maintained to optimise yield by size, for larger potential fillets. A two-pound fish yields 50% edible meat. Optical recognition systems could monitor average stock size per tank, and mechanically draw off smaller fish not following the growth curve, by variable mesh filters, thus isolating those individuals for separate intensive rearing. Different food supplements can enhance weight gain.

Part of the recycling process regularly draws fish into clear inspection tubes circulating through the basement, where growth rate segregation, or harvesting occurs. Once the peer group size is stabilised with maximum growth continuing, then the fish will not be filtered again until final harvesting is due.

© Jan Kaliciak 21-07-05 AquaUnit-01-v1.0