Feeding trial was conducted to evaluate impact of replacement of floating artificial feed (FF) with on-farm grown live Wolffia globosa (WG) in semi-intensive carp polyculture system of Catla catla (catla), Labeo rohita (rohu), Cirrhiunus mrigala (mrigal) and Osteobrama belangeri (pengba) on individual growth and health performance of fishes, overall net fish yield, feed utilization and economic performance of system. The juveniles of catla (10.7±0.54 g), rohu (11.8±0.49 g), mrigal (7.2±0.07 g) and pengba (14.4±0.24 g) were stocked in 15 outdoor cemented tanks (5m x 4m x 1m) at a combined stocking density of 1.5 fish m-2 in ratio of 20:30:20:30, respectively. Control tanks/treatments (T1) received FF (crude protein 25 %, diameter: 3mm) and the freshly harvested WG was utilized to replace the floating feed at levels of 25% (T2), 50% (T3), 75% (T4) and 100% (T5) on nitrogen/crude protein basis. The treatments were employed to tanks randomly in triplicates. Rohu exhibited significantly higher (p<0.05) mean weights (76-86 g) and specific growth rates (SGR; 2.35-2.55 % body weight gain d-1) for T2-T5 as compared to that of its counterpart in control (54 g & 1.78 % body weight gain d-1), respectively while pengba exhibited significantly higher final mean weight and SGR for T2 compared to rest of other treatments. Catla and mrigal did not show significant variations (p>0.05) in final mean weight among treatments, however, relatively higher mean weights were obtained for T2-T5 compared to that of their respective counterparts in T1. Overall net gain in biomass and net fish yield was significantly higher (p<0.05) for T2 and T5 compared to rest of other treatments. The feed utilization parameters showed remarkable variations with significantly improved (1.4-1.6 folds) values (p<0.05) of apparent feed conversion ratio, protein efficiency ratio and protein conversion ratio for T2-T5 as compared to T1 with best values for T5. Further, in general significant improvements (p<0.05) in haematological parameters including Haemoglobin, packed cell volume, RBC and WBC-contents were observed for T2-T5 as compared to that of T1, respectively. Digestive enzyme activities varied without any clear pattern. Partial budget analysis indicated remarkable improvements (p<0.05) in economic performance including 33%-77% reductions in feed cost per kg production and 1.4-1.7-fold increase in net profit for T2- T5 compared to that of T1 viz. feeding only with FF, respectively with best values for T5 viz. feeding exclusively with WG. Results indicated high potential of replacement of FF with WG for carps under semi-intensive polyculture.