Recirculation aquaculture system (RAS) with tilapia in a hydroponic system with tomatoes
2012
Vergote, N. | Vermeulen, J.
Aquaculture on land is one of worlds fastest growing business. Combination of aquaculture with horticulture has advantages. Emissions of waste water of recirculation systems for aquaculture could be reduced thanks to the re-use in recirculation systems for horticulture. Low value energy, not applicable in the heating process of greenhouses, is useful in the heating of the fish water. Other advantages are CO2 production/assimilation, nutrient release/uptake, double use of infrastructure, etc. In a greenhouse with a hydroponic culture of tomato and aquaculture system with tilapia was integrated. The nutrients coming from the fish-excrements were used in the tomato. The purpose was to monitor the parameters coming from the aquaculture in order to optimise the integration. In this pilot 890 plants of tomato were planted in rock wool and 2250 tilapia were introduced in 2×7.5 m3 watertank on 2 February 2009. The fish were fed depending on their weight. The water of the fish was kept between 25-30°C and monitored on its mineral content. Also the growth of the fish was monitored. The concentration of most of the minerals was too low, so an addition of these minerals before using it in tomato was necessary. A reduction of 50% of these nutrients was realised. A high content of Na+, Mn2+ and Cl- heightened the risk of accumulation and limited recirculation. Using fish-feed with lower Na+ content (pure vegetarian) implicates a lower feed conversion. For maximum integration, the amount of waste water need to be adjusted to the need of water caused by evapotranspiration. Starting both cultures in December, implicates a ratio of 1 m3 fish/100 m3 tomato. An earlier or later start has a worse ratio.
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