2019 ASHS Annual Conference

Along with world population increasing, reaching 9 billion in 2050, food demand becomes a huge concern around the world. Besides, increasing population and fast growing industrialization lead environment problem becoming more obvious and serious. Fish is an important protein source for human daily consumption, but rising fish causes a lot of wastes polluting our environment. It is not sustainable if fish waste were simply dumped away, since fish waste contain high nitrogen which can be uptake by plants. Aquaponic system as the combination of hydroponic production, aquaculture and bacteria has ability to convert fish wastes to nutrients for plants, as well as purify water simultaneously to provide both fish and edible plants for human needs. Typically, aquaculture specialist set pH 7 for coupled aquaponic system, because nitrifying bacteria can have better activity in pH range 7.2-7.8. Fish wastes contain ammonia (NH₃), and optimum living condition helps nitrifying bacteria to convert ammonia to nitrate (NO₃^-) which can be used for plants growth. In my experiment, three aquaponic system and three hydroponic system were used by setting pH as 6, 6.5 and 7 respectively. EC was maintained as 1.548±0.13 mS/cm, DO was maintained as 7.91±0.39 mg/L, and temperature was maintained as 22.106±0.684℃ for all pH treatments. Feeding rate was set as 1% biomass/day, and fishes were weighed every week to determine daily feeding amount accordingly. The whole experiment last one month. In result, in terms of leaf FW, aquaponic pH 6 showed 34.41% higher than aquaponic pH 6.5 and 34.78% higher than aquaponic pH 7. Similarly, aquaponic pH 6 showed 49.77% and 52.87% higher than pH 6.5 and pH 7 in leaf DW. Interestingly, in aquaponic system, pH 6 showed best FW and DW for leaf, stem and root of basil. Besides, aquaponic pH 6 showed no significant difference with hydroponic pH 6, except for FW stem and DW root. Hydroponic pH 6 showed significant higher FW stem than aquaponic pH 6. However, aquaponic pH 6 showed 47.22% higher DW root than hydroponic pH 6. Aquaponic pH 7 showed best fish growth, and pH 6 average fish weight was 12.57% lower. Overall, when considering about plants growth in coupled aquaponic system, pH 7 might not be a good choice, because pH 6 showed significant higher yield than pH 7. Based on the experiment, farmers can set pH wisely in coupled aquaponic system, since pH 6.5 toward 6 is better for plants to grow. High profit and short life cycle plants can be used in the system for higher return on investment. Further investigation of this study could determine effect of different pH setting for various plants species.