Effect of Ipom oea aquatica,as an Ecological Floating Raft,on Water Quality of Aquaculture Ponds

Effect of the ecological floating rafts on the water quality of intensive aquaculture ponds was studied.Ammonium nitrogen(NH+4-N),nitrite nitrogen(NO-2-N),nitrate nitrogen(NO-3-N),orthophosphate phosphorus(PO3-4-P),total nitrogen(TN),total phosphorus(TP)and CODMn were the major indicators for the determination of water quality.The water purification mechanism was studied as well.In the experiments under otherwise same conditions,three treatments were tested against the control.The pollutant contents in the pond water decreased in the order of control>5% Treatment>10% Treatment>20% Treatment.And,the removal rates on the above listed pollutants resulted from the 20% Treatment,the highest among three,were 42.82%,39.47%,43.8%,64.1%,46.57%,58.75% and 7.4%,respectively.The total yield of the 6-harvest floating plants ranged from 586.86 kg to 1 434.06 kg in the 667 m2 pond.For the 5%,10% and 20% treatments,1 643.5,988.2and 4 015.3g per 667m2 of TN,respectively,and 240.7,437.6and 587.9g per 667m2 of TP,respectively,were removed from the water. Meanwhile,the survival rate of the tilapia raised in the tested aquaculture pond improved significantly with the treatments.It appeared that cultivating Ipom oea aquatica in a tilapia pond could purify the pond water through eutrophication reduction.Specifically,a 20% of the artificial floating raft on a tilapia aquaculture pond could be recommended for implementation.