An experiment was conducted on the bio-efficacy of certain herbicides for controlling water hyacinth (Eichhornia crassipes) and its impact of herbicides on fish mortality. Three herbicides (Fernoxone @ 1.50 kg ha-1, Glycel or Round up @ 2.50 kg ha-1 and Gramoxone @ 1.50 kg ha-1) were tried, all are foliage applied herbicides. Three different fishes were tested such as common carp, mrigal and rohu. Among the herbicides applied, round up caused maximum reduction of plant height of 0.50, 1.00 and 1.00 cm; 2.75, 6.98 and 10.00g of biomass were obtained at 50 DAS on small, medium and large statures of E. crassipes. The cent percent chlorophyll content was recorded compared to control treatment at 28 DAS, whereas it cent percent mortality of E. crassipes at 35 DAS on small, medium and large statures of the weed. Similarly the same herbicides caused the least mortality percent of fishes 23.30, 16.60 and 20.00 on common carp, mrigal and rohu at 32 DAS, respectively compared to other herbicide treatments.