Control and utilization of inorganic nitrogen in intensive fish culture ponds

Abstract

One of the main obstacles toward the intensification of aquaculture systems is the accumulation of inorganic nitrogen in the water, A solution demonstrated in this work is to control inorganic nitrogen levels through the induction of microbial protein synthesis. This is achieved by adding a carbonaceous substrate, adjusted in a way so as to supply the needed carbon to immobilize all the non-utilized nitrogen. Inorganic nitrogen levels are reduced due to the resulting production of microbial protein. The in situ produced microbial protein is a substitute to the protein added with the feed. Fish growth in the treated ponds was higher than the growth in conventionally fed ponds. Protein utilization was doubled due to the recycling of nitrogen in the pond system, leading to diminution of the deleterious inorganic nitrogen accumulation. The price of feed was reduced to 50-67% of that common in conventional ponds, due both to replacement of protein and limited wash-out of feed.