VERTICAL SUBSTRATES IN BIOFLOC SYSTEMS AN INTERMEDIATE INTENSIVE AQUACULTURE SYSTEM  

The suspension of bioflocs in the water is essential in conventional biofloc systems. This necessitates the use of high energy water mixing, a condition that is often beyond the possibilities of small farmers. An alternative to the use of suspended biofloc systems was developed in the Hitide Seafarms, Tamil Nadu, India, by its owner Boriah Suryakumar.

The methodology is based on hanging plastic shade nets in the water, held by series of floats and anchors, preferably placed in front of a paddle wheel aerator. The vertical substrates adsorb organic detritus, serving as a base for the development of an aquatic biota, similar to that of bioflocs. The presence of the vertical substrates reduce the extent of organic sedimentation onto the bottom of the pond. The sedimentation is replaced by the accumulation of  the organic residues within the aerated water layer, this enabling an effective metabolism and recycling of feed waste in the pond. The biological processes in the pond is based upon the addition of molasses so as to maintain a C/N ratio of 10 in order to prevent excessive TAN concentration in the water.

Accumulated experience demonstrates that the placement of the vertical substrates helps in increasing shrimp growth rates, lower sludge accumulation, reduces FCR and reduces diseases occurrence.  It seems that the methodology demonstrated in Hitide Seafarms can be used by farmers, as such or as an intermediate system toward higher intensification, Further research and development in the farm is underway.