Credit: Nick James (Rivendell Hatchery – South Africa)
This tunnel grow-out tilapia farm is located in Grahamstown, South Africa. Red tilapia (O. mossambicus is the fish grown in this farm). Each greenhouse measures 46×8 meters. There are 20 tanks under the greenhouse of 7000 l each; water depth in the tanks is 60 cm.
The plastic cover of the greenhouse is a single layer of 200 micron. The plastic stays on all year, when inside temperature turns hot, the ventilation is sufficient to maintain the optimum temperature. This tunnel system raises water temp by 7C over ambient. During the coldest two winter months, an 18kw 3-phase heat pump is used and raises the whole system by additional 4 degrees Celsius.
The system is equipped with 1.5 kw air blower, sufficient mechanical and biological filtration, UV sterilization and 2×1.1 kw pumps capable to carry out changes of water every 2.5 hours.
Each 7000-l tank is initially stocked with 800 tilapia fingerlings of 1g, which is later thinned down as they grow to 400 of 500g harvest sized. Commercial locally manufactured floating tilapia pellets is used with diameters of 1, 2, and 3-mm. The production of a single tunnel as this one is more than 5 tons of market size tilapia per year (35.7 kg/m3) which seems economically feasible under the overall situation in South Africa.