Reclaiming Wolffia arrhiza as fish feed for the phytoremediation of aquaculture effluent

The aquaculture industry through the fisheries sector holds an important key aspect of food security. Despite its significance, it comes with environmental issues that cannot be avoided in most industrial activities, especially issues regarding water-related pollution. This study explores a novel dual-purpose approach, in which a floating species, Wolffia arrhizal, was applied for phyto-remediating aquaculture effluent and later followed by the evaluation of its potential as alternative fish feed. Different concentrations of contaminant loads were exposed to W. arrhiza plants for 7 days, and the best performance with removals of 15 % chemical oxygen demand (COD), 80 % biological oxygen demand (BOD), 99 % ammoniacal nitrogen (AN) and 94 % total suspended solids (TSS) were achieved in the treatment system using 0.1 g COD/g plant. The harvested plant biomass enriched with nutrients demonstrating strong potential for resource recovery within a circular economy framework, was then utilized in three separate fish feeding trials. Catfish were fed with 100 % commercial pallets; 50 % mixture of commercial pallets and 50 % W. arrhizal; and 100 % W. arrhiza. Results showed that W. arrhiza collected after phytoremediation treatment shows good potential as fish feed, but modification is needed in its formulation to ensure sufficient nutrient supply for fishes. This study highlights the dual potential of W. arrhiza as phytoremediator for aquaculture effluent and later being used as fish feed, contributing to both environmental protection and resource circularity in aquaculture.