Floating aquatic plants systems are an economically sustainable option for fish effluents treatment. A system of ponds with Azolla pinnata was evaluated at pilot scale as the treatment of a fish culture effluent, during the growth-fattening period. system was located on the fish farm The Yunga (Popayan, Colombia) and it consisted of two lines of five ponds in series, one with A. pinnata and the other without the aquatic plant; each pond was operated with a detention time of a day. assessment was conducted during the dry season. production of fresh Azolla ranged between 42 and 87 g/m 2 .d and protein content between 18,5% and 20,4%. removal efficiencies obtained in lines (with Azolla , without Azolla) were respectively 56% and 46% BOD 5 , 49% and 26% COD, 56% and 33% TSS, 28% and 36% TKN, -108% y 23% N-NH 4 + , 64% and 34% total phosphorus. best performance was of the system with Azolla. With only three ponds in series planted with A. pinnata are reached maximum efficiencies obtained in the removal of BOD 5 , COD, TSS and total phosphorus.