Credit for the photos: El-Sadig Arbab Hagar (Sudan), Samuel Simon Zigizo (South Sudan) and David Martin Sykora (Paraguay). Credit for the technical information: Ismael Radwan (project owner, Kafr El Sheikh, Egypt)
Photo A-1 shows the whole biological filter for a 240-m3 closed aquaculture project. Photo A-2 shows the plastic rings which are the main substrate in the filter, upon which the nitrifying bacteria (nitrosomonas and nitrobacter) naturally colonize. The pumping capacity of the project as shown in photo B is represented by two 15-kw electric pumps (one pump in operation while the second one is on standby). The discharge capacity of each pump is 6m3/minute which is sufficient to carry out the exchange of water at a rate of once/hour in the 24 production tanks which are hosted by a greenhouse. The water depth in the production tanks is kept at 50 cm to allow a high rate of water exchange having in consideration the pumping capacity of the project. The production capacity of this system ranges from 45 – 50 kg/m3 of 500-g size tilapia after a 6-month growing season when starting with about 5-g fingerlings. Because water used in the project is well water (warm water), and because the relative insulation provided by the greenhouse, more than a production cycle could be attained in a year. Feed used in this project is 32% protein commercial feed.