To test the nutrient uptake efficiency and CO2 uptake of two functional groups of floating plants, we grew the water fern Azolla filiculoides and duckweed (a mix of Spirodela polyrhiza, Lemna minor, and L. minuta) on wastewater effluent in a year-round experiment at a wastewater treatment plant. The floating plants were grown in cascading tanks of 300 L, containing either one single plant-type or both plant-types in different sequences. All four treatments were run in duplicate. We assessed nutrient removal efficiency for a full seasonal cycle (October - October) and with two different flow rates: 24 or 12 L h-1. To determine the climate impact of plant-mediated effluent polishing, we measured greenhouse gas fluxes (carbon dioxide, methane and nitrous oxide) on six occasions during the year. Furthermore, we constructed a model to assess the effect of hydraulic residence time and harvesting frequency on phosphorus removal efficiency.