VETIVER on AQUAPONICS: Improving Water Quality for the Rearing of Pangasius hypothalamus Fingerlings in Concrete Tank Using Vetiver Grass Chrysopagon zizanioides

Abstract

Aquaponics is characterized by the symbiotic growing of plants and aquatic animals in one infrastructure and system to meet the water and nutrients needs simultaneously. The water used to culture the fish contains organic waste that can be used for plant growth and development. The plant can serve as bio-filter for the improvement of water for fish production. Vetiver is a grass that grows with long fibrous root system that can filter and absorb plant nutrients and hazardous chemical substances in the environment. Its cultivation can help prevent pollution and allow water source to be acceptable for culturing fishes and other minor fishery products. The study “Vetiver System on the Intensive Culture of Pangasius hypophthalamus in Circular Tank” was conducted to evaluate the physicochemical condition of the water during the growing period of pangasius under intensive culture in circular tanks with the application of vetiver grass system. The physicochemical parameters are indicative of the quality of water in the culture system for growth and survival of the organisms under culture. In this intensive culture system nine (9) units of circular concrete tanks (6.0 cu. m capacity) stocked with Pangasius hypophthalamus fingerlings (7 to 10 grams average body weight) at varying stocking rates of 100. 75, 50 fish per cubic meter of water, as study treatments using three tanks as replications designated as Treatment I (tanks 2,4,9) stocked with 300 fish, Treatment II (tanks 1,3,7) with 450 fish, Treatment III (tanks 4,6,8) with 600 fish. Commercial floating pellets were fed to the stocks twice a day. Water management includes daily water exchanges, aeration, and monitoring of water quality. Results of monitoring conducted before the application of vetiver pontoon shows that the temperature (26 to 30 degree), pH (7 to 8) and dissolve oxygen (>2 ppm) were within the desired level while the ammonia (>1 ppm) of the water in the tanks fluctuates towards undesirable levels. The fish increment growth was 6.53 grams and survival rate of about 88% (1977 out of 2240) of pangasius fingerlings initial stocks. The vetiver pontoon system gave a positive effect as it have help improved the water quality that enhanced the growth and survival of pangasius, reduced water requirements and discharges of polluted water in the environment within the thirty days application. The dissolved oxygen content of tank water 4.5 to 4.8 ppm was within the desirable level for the fish respiration and organic waste decomposition in the system. Likewise the temperature (26.9 to 27.1 °C) readings and the pH range (7.7 to 8.1) were within the desirable levels. The ammonia (NH3) levels were maintained at 0.6 ppm which rendered good quality water for the growth of pangasius fingerlings and vetiver grass. Pangasius fingerlings weight increment was 7.3 grams and survival rate was high at 93% (1838 out of 1977). The value of daily water exchanges were reduced from 3 cu. m to about 1.5 to 1.74 cu. m after the application of vetiver system. Some problems were encountered such as death of fish that get trapped in the pontoon, clogging of pontoon nets with floating feeds and dirt, presence of insect larvae on the leaves of vetiver, and foul odor of the bamboo pontoons. A similar study is recommended to validate the results obtained in this trial and to be conducted with longer detention period of a modified vetiver pontoon design for tank culture system.