| Summary: | In the present study, artificial floating islands (AFIs) have been tested as a methodology for reducing nitrogen and phosphorus loads from tilapia fishponds. Artificial floating islands are a variation of constructed wetlands (CWs), which are efficient in removing aquaculture wastewater, but they occupy at least 10 % of the production area. Based on the hypothesis that AFIs could be low-cost and efficient for removing nutrients from production fishponds, it was tested the efficiency of AFIs colonized by Eichhornia crassipes for nutrient removal in Nile tilapia fishponds. The experiment was done in two semi-intensive production systems during the grow-out period of tilapia, comprising one production cycle. It was completely randomized with two treatments (with and without AFIs). The water temperature, dissolved oxygen, electrical conductivity, pH, turbidity (NTU), and concentrations of total nitrogen (TN) total inorganic nitrogen (TIN), total phosphorus (TP) and orthophosphate (P-PO4) were analyzed fortnightly in the fishpond affluent and effluent. The mean water temperature, dissolved oxygen, conductivity, pH and DO did not differ between fishponds. The exported load (TN, TIN, TP and P-PO4) from AFI fishponds was lower than from system without artificial floating islands (WAFIs). The AFIs improved a lot the effluent water quality. It is necessary to better estimate the minimum area required for AFIs implementation, increasing the total nutrient removal, especially of phosphorus. The hydraulic retention time of the fishpond must be better controlled, allowing phytoplankton establishment, and thus favoring the phosphorus removal. In addition, associating the AFIs with polyculture production systems can ensure better use of the feed offered, increasing the production per productive area and removing surplus nutrients more efficiently.
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