The macrophytes enrich the water with oxygen and help to remove nutrients. The zeolite is also a natural way to combat pollution. The aim of this study was to investigate the effectiveness in waste water treatment process in RAS, applying filter with natural zeolites and macrophytic plants from genus Lemna and Elodea. The temperature and pH were measured daily with a portable combined meter in the newly constructed control and experimental RAS. Ammonium, nitrite, nitrate, total nitrogen and phosphor us were measured spectrophotometrically. At the end of the trial the fish were weighed and specific growth rate and FCR (feed conversion ratio) were calculated. The addition of zeolite and macrophytic plants as a part of filtration system of experimental RAS, decreased significantly the quantity of nitrogen and phosphorus compounds, compared to their amount in conventional one. The better water quality in experimental system, due to the presence in the filter of zeolites and macrophytic plants, influenced positively the growth of rainbow trout and feed utilization.