We evaluated the bioconversion of domestic wastewater into protein biomass through duckweed based ponds and fish farming in a pilot recirculating system. Duckweed average production reached up to 38.17 t ha-1 year-1 (dry matter), with crude protein and fiber content of 38.03% and 16.17%, respectively. Regarding fish growth parameters, fish fed commercial feed and pelletized duckweed did not presented statistical difference, which can be considered the most relevant result obtained. Tilapia final average weight, feed conversion rate and specific growth rate, when fed pelletized duckweed, were similar to values found with commercial feed. Therefore, duckweed production in wastewater can be a feasible alternative for tilapia farming, reducing feeding production costs.